'. 


A  LABORATORY  OUTLINE 

OF 

SMITH'S 
INTERMEDIATE  CHEMISTRY 


SMITH'S 
INTERMEDIATE    CHEMISTRY 

REVISED   AND    REWRITTEN   BY 

JAMES  KENDALL 

AND 

EDWIN  E.  SLOSSON 
566  pp.     With  15  illustrations  and  125  cuts. 

NEW  YORK,  THE  CENTURY  CO. 


A  LABORATORY  OUTLINE 

OF 

SMITH'S 

INTERMEDIATE  CHEMISTRY 

BY 

JAMES   KENDALL 

PROFESSOR  OF  CHEMISTRY,  COLUMBIA  UNIVERSITY 


NEW  YORK 

THE  CENTURY  CO. 
1922 

X 


COPYRIGHT,  1922,  BY 
THE  CENTURY  C(X 


PRINTED  IN  U.  S.  A. 


**•> 


PREFACE 

This  laboratory  outline  is  intended  to  accompany  the  revised 
edition  of  Alexander  Smith's  Intermediate  Text  Book  of  Chem- 
istry. It  includes  elementary  experiments  and  some  experi- 
ments from  Alexander  Smith's  Laboratory  Outline  of  College 
Chemistry.  Many  of  the  experiments  are  given  in  full  detail, 
so  that  they  can  be  used  by  students  who  are  taking  chemistry 
for  the  first  time. 

JAMES  KENDALL 
New  York,  May,  1922. 


CONTENTS 


1.  Substances  and  Properties 1 

2.  Capacities  of  Vessels 2 

3.  Weighing  and  Density 3 

4.  Changes  in  Metals  Heated  in  Air 5 

5.  Mixtures  and  Compounds 6 

6.  Oxygen  —  Preliminary 8 

7.  Glass-working 9 

8.  Oxygen  —  Preparation  and  Properties 10 

9.  Hydrogen  —  Preliminary 12 

10.  Hydrogen  —  Preparation  and  Properties 14 

11.  Water  —  Physical  Properties 15 

12.  Hydrates 17 

13.  Quantitative  Measurement  of  Water  of  Hydration       .     .  18 

14.  Weight  of  22.4  Liters  of  Oxygen 19 

15.  Atomic  and  Molecular  Weights 21 

16.  Composition  and  Formula  of  Nickel  Sulphide      ....  22 

17.  Composition  and  Formula  of  Oxide  of  Tin      .....  23 

18.  Solvents  and  Solubility 24 

19.  Solubility  and  Temperature.    Saturation 26 

20.  Hydrogen  Chloride  —  Preparation  and  Properties   ...  28 

21.  Chlorine  —  Preparation  and  Properties 30 

22.  Sodium  Hydroxide 31 

23.  Properties  of  Acids 32 

24.  lonization  of  Acids,  Bases,  and  Salts 34 

25.  Ionic  Materials       36 

26.  Equilibrium   Between  Undissociated  Substance  and  its 

Ions       37 

27.  Double  Decompositions  Between  Electrolytes  in  Solution  38 

28.  Bases  and  Acids 40 

29.  Neutralization 41 

30.  Solution  of  an  Insoluble  Base  by  a  Strong  Acid  ....  42 

31.  Displacement 43 

32.  Non-Ionic  Actions       44 


viii  CONTENTS 

EXERCISE  PAGE 

33.  Titration  of  Bases  and  of  Acids 45 

34.  Bromine .  47 

35.  Iodine 48 

36.  Comparison  of  the  Halogen  Compounds 50 

37.  Valence  of  a  Metd  by  Displacement 51 

38.  Salts •    .     .  56 

39.  Chemical  Equilibrium  in  Double  Decomposition      ...  57 

40.  Hydrogen  Peroxide 57 

41.  Hypochlorous  Acid.    Bleaching 59 

42.  Forms  of  Sulphur 59 

43.  Sulphides  of  Metals 61 

44.  Hydrogen  Sulphide 61 

45.  Sulphur  Dioxide 63 

46.  Sulphurous  Acid 64 

47.  Sulphuric  Acid 65 

48.  Percentage  of  Oxygen  in  Air 66 

49.  Carbon  Dioxide  in  Air  and  in  the  Breath   ......  67 

50.  Ammonia       68 

51.  Hydroxide  and  Salts  of  Ammonium 70 

52.  Nitric  Acid 71 

53.  Nitric  Oxide 72 

54.  Nitrous  Oxide 74 

55.  Phosphine  and  Phosphoric  Acid 75 

56.  Arsenic  Trioxide 76 

57.  Graphite .  77 

58.  Carbon  Dioxide  by  Oxidation 77 

59.  Carbon  Dioxide  —  Preparation  and  Properties    ....  78 

60.  Carbon  Monoxide 79 

61.  Hydrocarbons     . 80 

62.  Flame 82 

63.  Borax  Bead  Tests 83 

64.  Sodium  Bicarbonate.    Acid  Salts       84 

65.  Hydrolysis 85 

66.  Potassium  Nitrate  —  Preparation 85 

67.  Recognition  of  Substances  I 87 

68.  Recognition  of  Substances  II  (Negative  Radicals)    ...  88 

69.  Calcium  Oxide  and  Hydroxide 90 

70.  Hard  Water 91 

71.  Flame  Tests  (Positive  Radicals) 92 

72.  Starch  and  Sugars .  93 

73.  Agriculture.    Acid  and  Alkaline  Soils 94 


CONTENTS  ix 

EXERCISE  PAGE 

74.  Fertilizers 95 

75.  Fermentation 96 

76.  Acetic  Acid 97 

77.  Destructive  Distillation  of  Wood  and  Coal 98 

78.  Wood  Charcoal  and  Bone  Black 99 

79.  Tests  for  Food  Components 100 

80.  Food  Components  of  Milk 101 

81.  Food  Components  of  Flour 102 

82.  Analysis  of  Baking  Powder  (Qualitative) 103 

83.  Esters.    Soap 104 

84.  Colloidal  Suspensions 105 

85.  How  Soap  Cleanses 107 

86.  Compounds  of  Magnesium 108 

87.  Aluminum  Hydroxide.    Alum 108 

88.  Dyeing 109 

89.  Reactions  of  Iron  Compounds       110 

90.  Compounds  of  Lead.    White  Lead 112 

91.  Separation   of    Lead,    Mercury    and   Silver    (Metals   of 

Group  I) 112 

92.  Displacement  of  Metals.    Couples 114 

93.  Manganese  and  Chromium  .     .     . 115 

94.  Identification  of  Metals  in  Group  II 116 

95.  Identification  of  Metals  in  Group  III     .     .     .   • .     .     .     .  118 

96.  Identification  of  Metals  in  Groups  IV  and  V       ....  119 

97.  Recognition  of  Substances  III  (Metallic  Elements)       .     .  120 

APPENDIX 

I.   Tension  of  Aqueous  Vapor 122 

II.   Degrees  of  lonization  in  0.1  N  Solution 123 

III.  Apparatus  —  Individual 123 

IV.  Apparatus  —  General 124 

V.   Materials t     .  125 


GENERAL  INSTRUCTIONS 

Read  the  "Regulations"  posted  in  the  laboratory.  Read 
also,  attentively,  the  following  notes : 

Note  1 .  • —  Provide  yourself  with  a  note-book  and  make  a 
careful  permanent  record  immediately  after  each  experiment. 
Enter  the  numbers  and  titles  of  the  exercises  of  the  outline 
systematically.  State  (1)  what  you  did,  if  anything  beyond 
the  directions,  but  do  not  copy  the  printed  directions  them- 
selves, (2)  what  you  observed,  (3)  what  conclusions  you  drew. 
A  sketch  of  the  apparatus  will  enable  you  to  recall  the  circum- 
stances of  the  experiment,  if  later  reference  to  it  is  necessary. 
This  note-book,  when  called  for,  is  to  be  handed  in  for  inspection. 

The  blank  pages  in  this  Outline  are  not  intended  for  the  final 
notes.  They  may  be  used  for  individual  suggestions  given  by 
the  instructor,  preliminary  notes,  record  of  weighings,  etc. 

Note  2.  —  Whenever  an  interrogation  point  or  a  direct  ques- 
tion appears,  a  corresponding  observation  or  answer  should  ap- 
pear in  the  note-book.  The  "(?)"  indicates  something  to  be 
observed  and  recorded. 

Note  3.  —  The  very  numerous  questions  asked  in  the  course 
of  this  outline  are  intended  to  be  answered,  not  by  speculation, 
but  by  careful  observation  and  reasoning  based  on  the  results 
of  this.  Very  often  the  student  will  find  it  necessary  to  devise 
and  carry  out  further  experiments  of  his  own  before  a  satis- 
factory answer  is  obtained.  When  a  question  occurs  to  you, 
endeavor  by  reflection  and  study  to  answer  it  yourself  before 
consulting  an  instructor. 

Note  4.  —  In  many  cases  the  work  outlined  could  not  in  itself 
furnish  the  basis  for  an  answer,  and  fuller  investigation  of  the 
point  would  require  work  beyond  the  time  or  ability  at  the  dis- 
posal of  the  beginner.  Such  questions  are  distinguished  by 
references  to  Alexander  Smith's  Intermediate  Text  Book  of 
Chemistry  (revised  edition),  the  page  where  the  necessary  in- 
formation may  be  obtained  being  indicated  in  bold  type  between 
square  brackets.  This  text  should  be  consulted,  however,  only 

i 


ii  GENERAL  INSTRUCTIONS 

after  the  experiments  have  been  made  and  the  notes  written  up 
as*  far  as  possible.  Cross-references  to  other  experiments  in 
this  laboratory  outline  are  given  in  ordinary  type. 

Note  5.  —  When  a  chemical  change  has  been  observed  the 
equation  should  always  be  given  in  the  notes,  but  an  equation 
alone  is  never  a  sufficient  record. 

Note  6.  —  Where  the  word  [Instructions]  appears,  consult  the 
instructor  before  going  further. 

Note  7.  —  In  quantitative  experiments,  marked  [Quant.], 
use  the  finer  balance;  in  all  other  cases  the  rough  scales  in  the 
laboratory. 

Note  8.  —  The  expression  [Storeroom]  indicates  that  the 
necessary  apparatus  is  not  included  in  the  individual  outfits. 

Note  9.  —  When  the  word  [HOOD]  appears,  the  operation  is 
not  to  be  conducted  in  the  open  laboratory.  The  apparatus 
is  to  be  placed  at  once  close  to  the  desk-ventilator,  or  trans- 
ferred to  the  hood. 

Note  10.  —  Where  exact  quantities  are  not  indicated,  very 
small  amounts  of  solutions  (1  c.c.  or  less)  should  be  taken. 
This  advice  is  given,  partly  to  secure  saving  of  material,  but 
chiefly  to  avoid  the  waste  of  time  which  working  with  large 
quantities  always  entails. 

Note  11.  —  To  obtain  the  necessary  chemical  substances,  if 
the  chemicals  are  not  furnished  in  "kits"  to  each  student,  do 
not  carry  the  bottles  from  the  side-shelf  to  the  desk.  Bring 
a  clean  test-tube  for  liquids  and  a  watch-glass  for  solids.  For 
the  latter,  a  piece  of  paper,  provided  near  the  side-shelf, 
may  also  be  used.  When  too  much  of  any  reagent  has  been 
taken,  do  not  return  it  to  the  bottle. 

Note  12.  — The  chemicals,  if  on  a  side-shelf,  are  divided 
into  two  sets,  each  arranged  alphabetically  according  to  the 
scientific  names.  The  first  set  consists  of  solids  in  small  bottles, 
the  second  of  liquids.  The  bottles  and  their  places  are  num- 
bered consecutively  to  facilitate  accurate  replacement,  and 
scrupulous  care  must  be  taken  not  to  disarrange  them.  Read 
the  labels  attentively,  as  there  are  frequently  several  kinds  of  the 
same  substance  (e.g.,  pure,  commercial,  dilute,  concentrated, 
and  normal). 

All  materials  are  supplied  through  the  storeroom  service. 
Do  not  therefore  take  side-shelf  bottles,  when  found  empty,  to 
the  instructor,  but  to  the  storekeeper  for  refilling. 


GENERAL  INSTRUCTIONS  iii 

Note  13.  —  The  expression  [From  Instructor],  however,  in- 
dicates one  of  a  few  special  substances  for  which  the  student 
must  apply  to  an  instructor. 

Note  14.  —  The  bottles  on  the  desk,  if  there  are  any,  con- 
tain certain  substances  which  are  frequently  used.  These 
substances  will  not  be  found  on  the  side-shelf. 

Note  15.  —  When  any  acid  gets  upon  the  clothing,  apply 
ammonium  hydroxide  solution  at  once. 

Note  16.  —  Burns,  whether  caused  by  contact  with  hot 
objects,  by  acids,  or  by  corrosive  liquids  like  bromine,  are 
rubbed  gently  with  a  paste  of  sodium-hydrogen  carbonate  and 
water.  All  burns,  save  the  slightest,  must  afterwards  be  dressed 
with  an  aqueous  solution  of  boric  acid  (half -saturated)  to  prevent 
infection.  Obtain  the  assistance  of  an  instructor. 

Cuts  must  be  washed  in  running  water  and  dressed  with 
boric  acid  as  above,  or  with  lanolin  containing  2  per  cent  of  boric 
acid. 

Note  17.  —  All  students  work  independently,  except  where 
cooperation  of  two  students  is  expressly  directed. 


LABORATORY  OUTLINE  OF 
INTERMEDIATE  CHEMISTRY 


EXERCISE  1 
SUBSTANCES  AND  PROPERTIES 

Object:  To  observe  and  record  the  properties  of  some  substances. 
Apparatus:  Graduated  cylinder.   Test-tubes.    Rack.    Evaporating 

dish.     Wire  gauze. 
Materials:  2   pieces  each  of  white  cotton  cloth,*  white  mixed 

goods,*  and  woolen  yarn.     Sodium  hydroxide  (solution,  2%). 

Eosin  or  Acid  Green  (solution,  0.5%).     Sulphuric  acid  (cone.). 

a.  Place  60  c.c.  of  sodium  hydroxide  solution  in  the  graduated 
cylinder.  Divide  the  liquid  equally  between  three  test-tubes, 
immerse  the  pieces  of  cotton,  wool,  and  mixed  goods,  one  in 
each  tube,  and  set  the  tubes  in  the  rack.  Attach  the  Bunsen 
burner  by  means  of  rubber  tubing  to  a  gas  connection,  close  the 
air-holes  at  the  base,  and  light.  Now  open  the  air-holes  gradu- 
ally and  note  the  effect  upon  the  flame  (?). 
Close  the  air-holes  again,  and  hold  a  porcelain 
dish  in  the  flame.  What  is  deposited  on  the 
dish?  What  is  the  proximate  cause  of  the  dif- 
ference in  the  two  flames?  When  using  the 
burner  for  heating  purposes,  always  regulate 
the  air  supply  so  as  to  get  a  noiseless,  non- 
luminous  flame.  Heat  the  contents  of  the 
tubes  one  after  another  to  the  boiling  point,  FIG.  1 

holding  each  by  means  of  a  piece  of  paper 
folded  so  as  to  give  four  thicknesses  (Fig.  1).    Then  keep  one 
above  the  flame,  at  the  boiling  point,  but  not  bumping,  for  two 

*  Before  use,  the  cloth  must  be  treated  as  in  Ex.  88  o,  to  remove 
sizing. 

1 


2  CAPACITIES  OF  VESSELS 

minutes,  then  the  second,  then  the  third,  then  the  first  again 
and  so  forth.  When  the  material  in  one  of  them  has  all  dis- 
solved, examine  all  three.  Record  the  results  as  follows: 

DISSOLVED  IF  CHANGED,  APPEARANCE  OF 

How  LIQUID 

Cotton: 
Wool: 
Mixed  goods: 

b.  Place  the  wire  gauze  on  a  ring  on  the  ring  stand  (Fig.  2). 

Fill  the  evaporating  dish  three-fourths  full  of  water,  add  two 
drops  of  concentrated  sulphuric  acid,  place  it  on  the 
gauze  and  heat  to  boiling.  Add  10  c.c.  of  the  solution 
of  the  dye  provided.  Immerse  one  sample  each  of  the 
cotton,  wool,  and  mixed  goods,  so  that  they  are  com- 
pletely covered.  Stir  with  the  glass  rod,  and  heat 
for  2  or  3  minutes.  Pour  the  liquid  into  the  sink  and 
wash  the  materials  thoroughly  in  clean  water.  Note 
the  effect  on  each  (?). 
FIG  2  c.  If  a  microscope  is  available,  place  shreds  of 
each  sample,  after  drying,  on  a  strip  of  glass  and 

describe  the  appearance  of  the  fibers  as  to  structure  (?)  and 

color  (?). 

d.  Record  the  specific  properties  of  wool  and  of  cotton,  both 
those  observed  in  these  experiments  and  those  already  known 
to  you:    natural  color  (?),  natural  structure  (?),  solubility  in 
water  (?),  solubility  in  sodium  hydroxide  solution  (?),  effect  of 
dyes  (?). 

e.  Smooth  out  the  pieces  of  cloth  and  yarn  on  glass  plates, 
or  on  bottles,  to  dry,  and  mount  them  in  your  notes. 

/.  Wash  out  the  test-tubes  and  dish  thoroughly  and  put 
them  away.  Throw  scraps  of  cloth  into  the  jars,  and  not  into 
the  sink.  Cleaning  up  in  this  way  follows  every  experiment 
hereafter. 

EXERCISE  2 

CAPACITIES  OF  VESSELS 

Object:   To  learn  the  capacities  of  several  vessels  by  measuring  the 
volumes  of  liquids  they  hold. 


WEIGHING  AND  DENSITY  *6 

Apparatus:  Graduated  cylinder.    Test-tube.     Evaporating  dish. 

Flask. 
Materials:  2  small  rubber  bands. 

a.  Place  water  in  the  graduated  cylinder  up  to  the  5  c.c. 
mark.    The  lowest  point  of  the  meniscus  must  be  opposite  the 
mark  (Fig.  3).    Pour  this  water  into  a   test-tube 

and  place  a  narrow  rubber  band  round  the  test-tube 

at  the  level  of  the  lowest  point  of  the  meniscus. 

Measure  and  place  in  the  test-tube  a  second  5  c.c. 

of  water.    Mark  with  a  second  rubber  band  the  new 

position  of  the  meniscus.     Make  in  your  note-book 

a  full-size  drawing  of  the  test-tube,  and  show  the 

positions  of  the  bands.     Observe  carefully  the  pro-       FIG.  3 

portions  of  the  tube  occupied  by  5  c.c.  and  by  10  c.c. 

of  water,  so  that  when  directed  in  future  to  use,  say,  "about  10 

c.c."  of  a  liquid  or  a  solid  you  may  be  able  to  judge  the  amount 

by  the  eye. 

b.  Fill  the  graduated  cylinder  with  water  to  the  highest  mark. 
Fill  the  evaporating  dish  with  water  from  the  cylinder,  note  the 
volume  of  water  remaining,  and  subtract  to  learn  the  capacity 
of  the  dish.    Record  all  the  figures  in  your  notes.    Repeat  with 
the  flask. 

c.  What  is  the  weight  of  1  c.c.  of  water?    What  weights  of 
water  do  the  evaporating  dish  and  the  flask  hold? 

EXERCISE  3 
WEIGHING  AND  DENSITY 

Object:  To  learn  to  weigh  and  to  learn  how  to  measure  densities. 
Apparatus:   Balance  (one  for  every  10  pupils).    Evaporating  dish. 

Graduated  cylinder.     20  c.c.  pipette. 
Materials:  Roll  sulphur.    Sodium  chloride  (sat.  sol.). 

a.  Use  of  the  Simple  Balance  [Instructions.  Quant.].  By 
turning  the  screw  attachment  in  front  of  balance  case,  release 
the  beam  and  pans,  allowing  the  beam  to  swing.  Observe  the 
excursions  made  by  the  pointer.  Divide  by  two  the  total 
divisions  covered  by  the  pointer  in  one  full  swing,  and  count 
off  from  either  end  of  the  swing  the  divisions  which  this  number 
designates,  thus  finding  the  position  of  the  true  zero  point.  The 


4  WEIGHING  AND  DENSITY 

beam  must  swing  freely  during  the  observation:  the  zero  is 
never  to  be  read  with  the  beam  at  rest. 

This  observed  zero  point  may  lie  a  little  to  the  right  or  to  the 
left  of  the  marked  zero.  Note  down  its  distance,  in  scale 
divisions,  from  the  marked  zero.  If  it  lies  to  the  right  prefix 
to  the  number  of  divisions  the  minus  (  — )  sign;  if  to  the  left  the 
plus  (+)  sign.  The  zero  of  any  one  balance  changes,  and  must 
be  redetermined  every  time  a  weighing  is  made. 

Place  a  10  g.  weight  in  each  pan  [Note  1,  below],  and  deter- 
mine the  zero  as  before.  Add  the  0.01  g.  weight  to  the  right- 
hand  pan,  and  find  the  reading  about  which  the  pointer  now 
oscillates.  The  difference  in  reading  between  this  point  and  the 
last  determined  zero  point  gives  the  deflection  due  to  the  0.01  g. 
weight.  It  may  be  used  for  estimating  weights  less  than  0.01  g. 
Thus,  suppose  the  0.01  g.  weight  causes  a  deflection  of  5  divi- 
sions to  the  left  (+5).  When  some  body  is  being  weighed, 
if  the  deflection  is  +  1,  then  3-  of  the  0.01  g.  or  0.002  g.  must  be 
subtracted  from  the  sum  of  the  weights. 

Note  1. — Great  care  must  be  taken  in  the  use  of  the  balance 
and  weights.  The  pans  of  the  former  must  be  let  down  upon  their 
supports  when  not  in  use  and  every  time  weights  or  other  objects 
are  to  be  added  or  removed.  All  objects  to  be  placed  upon  the  pans 
must  previously  be  carefully  cleaned  and  dried.  Solids  are  placed 
upon  a  watch-glass  or  upon  a  piece  of  glazed  paper,  and  never  directly 
upon  the  pans.  The  weights  must  be  lifted  from  their  case  by  means 
of  forceps,  never  by  the  fingers.  They  are  usually  placed  on  the 
right-hand  pan,  the  objects  to  be  weighed  on  the  left. 

Note  2. — In  reckoning  results,  count  first  by  the  places  vacant 
in  the  box,  and  check  by  counting  the  weights  themselves.  This 
will  enable  you  to  avoid  the  commonest  error  in  weighing,  namely, 
miscounting  the  weights.  Finally  record  the  weights  in  the  note- 
book, or  laboratory  outline,  and  never  upon  loose  sheets  of  paper, 
as  loss  of  the  latter  will  necessitate  a  repetition  of  the  entire  experi- 
ment. 

b.  Weigh  an  evaporating  dish  (dry)  on  the  balance  to  the 
nearest  decigram  (0.1  g.)  and  record  the  weight. 

Place  in  the  dish  about  10  g.  of  pieces  of  roll  sulphur  (no 
particles  or  dust  of  sulphur),  and  weigh  once  more.  Record  the 
weight.  The  difference  (?)  is  the  exact  weight  of  the  sulphur 
actually  taken. 


~^ 


^  ,  C 


CHANGES  IN  METALS  HEATED  IN  AIR  5 

Place  in  the  graduated  cylinder  exactly  20  c.c.  of  water. 
Incline  the  cylinder  and  allow  the  sulphur  gently  to  slide  into 
the  water  in  the  cylinder.  Read  and  record  on  the  total  volume. 
The  increase  (?)  is  the  volume  of  the  sulphur.  Calculate  from 
your  data  the  weight  of  1  c.c.  of  sulphur  (?).  This  is  the  density 
of  the  sulphur. 

c.  Record  the  specific  physical  properties  of  sulphur  which 
you  have  observed,  namely:    color  (?),  crystalline  or  not  (?), 
brittle  or  malleable  (?),  density  (?),  soluble  in  water  or  not  (?). 

d.  Wipe  out  the  evaporating  dish,  and  use  the  weight  already 
recorded.    Fill  a  20  c.c.  pipette  to  the  mark  with  a  saturated 
solution  of  common  salt,  allow  this  solution  to  run  gently  into 
the  dish,  and  weigh  again  (record).    The  difference  (?)  is  the 
weight  of  the  brine.    Calculate  the  density  of  the  brine  (?). 

EXERCISE  4 
CHANGES  IN  METALS  HEATED  IN  AIR 

Object:   To  observe  changes  in  properties  when  a  new  substance  is 

formed  by  the  action  of  oxygen  from  the  air. 
Apparatus:   Balance.     Porcelain     crucible.     Pipe-stem     triangle. 

Meter  stick  (one  for  class).     Piece  of  iron  wire,  No.  26. 
Materials:  Copper  wire  (No.  30).    Tin  foil. 

a.  Take  about JTmeters  of  copper  wire  (No.  30),  wind  it  round 
a  pencil,  and  place  the  coil  in  the  porcelain  crucible.    Weigh 
the  whole  on  the  balance,  counting  the  weights  as  in  3  a  (record) . 
Place  the  crucible  (uncovered)  in  the  pipe-stem  triangle  (Fig.  4) 
and  heat,  at  first  gently  and  then  with  the  full  Bunsen 

flame,  for  fifteen  minutes.  Now  lower  the  flame  to 
permit  the  crucible  to  cool  gradually,  and  finally 
remove  it.  Weigh  the  crucible  when  cold  (record). 
To  what  is  the  difference  in  weight  due? 

Examine  the  coil  (?),  and  bend  the  remains  of  the 
wire  (?).  Name  the  product,  and  make  a  condensed 
statement  [9]  of  the  change.  Record  the  specific 
physical  properties  of  the  copper  and  of  the  product, 
namely:  color  (?),  appearance  (metallic  or  other-  FIG.  4 
wise  ?),  pliability  or  brittleness  (?)  of  each. 

b.  Fold  up  about  10  cm.  square  of  tin  foil  and  place  it  in  the 
porcelain  crucible.    Weigh  the  whole  on  the  balance  (record) 


6  MIXTURES  AND  COMPOUNDS 

and  proceed  as  in  a,  par.  1.  Stir  the  tin  occasionally  with  a  short 
piece  of  iron  wire,  but  be  careful  to  keep  all  the  material  in  the 
crucible.  Describe  what  you  observe  (?). 

Name  the  product  (?)  and  make  a  condensed  statement  [9] 
of  the  change.  Record  the  specific  physical  properties  of  the 
tin  and  of  the  product,  namely,  color  (?),  appearance  (?),  plia- 
bility (?)  of  each,  and  melting  point  of  tin  [507]  (?) 

EXERCISE  5 
MIXTURES  AND  COMPOUNDS 

Object:  To  learn  how,  by  observing  properties,  to  distinguish  between 
mixtures  and  compounds. 

Apparatus:  Magnet.  Test-tubes.  Funnel.  Evaporating  dish. 
Mortar.  Trip  scales.  Bunsen. 

Materials:  Iron  powder.  Carbon  disulphide.  [CAUTION:  Ex- 
tinguish Bunsen  flame  while  using  this.]  Filter-paper.  Hydro- 
chloric acid  (dil.).  Sulphur. 

a.  The  Properties  of  Iron.  Place  about  0.5  c.c.  of  iron 
powder  on  a  piece  of  paper.  Examine  it  (?).  Draw  one  pole 
of  a  magnet  across  the  lower  surface  of  the  paper,  noting  the 
behavior  of  the  iron  (?). 

Transfer  half  the  iron  to  a  dry  test-tube,  add  2  c.c.  of  car- 
bon disulphide  [CARE!  Inflammable!  Do  not  handle  near 
a  flame],  and  shake.  Fold  a  filter-paper  once,  and  then  again 
at  right  angles  to  the  straight  edge.  Open  the  paper  as  a  cone, 

with  a  triple  layer  of 

OX^""X     ^^^     \\    /    paper  on  one  side  and  a 
•  '       XA        \/      single  layer  on  the  other, 

and  place  it  in  a  glass 
y        funnel   (Fig.  5).     Place 
jrIGf  5  the  funnel  in  one  ring  of 

the  iron  stand,  place  the 

evaporating  dish  below  the  end  of  the  stem,  and  pour  the  con- 
tents of  the  test-tube  on  to  the  paper.  When  the  liquid  has 
run  through,  open  up  the  paper,  so  that  the  remaining  liquid 
may  evaporate.  Place  the  dish  in  a  draft,  away  from  all  flames, 
where  its  contents  may  evaporate  also.  While  evaporation  is 
going  on,  proceed  with  the  operations  described  in  the  follow- 
ing paragraphs.  When  the  paper  and  dish  are  dry,  examine  the 


MIXTURES  AND  COMPOUNDS  7 

residue  on  the  paper  (?)  and  draw  the  pole  of  the  magnet  across 
the  lower  surface  of  the  paper  (?).  Examine  the  dish  (?).  Is 
iron  soluble  in  carbon  disulphide  (?). 

Place  the  other  half  of  the  iron  in  a  test-tube,  add  a  few  drops 
of  hydrochloric  acid  and  note  the  odor  [52]  or  absence  of  odor. 

Record  the  properties  of  iron,  namely:  color  (?),  effect  of 
magnet  (?),  solubility  in  carbon  disulphide  (?),  effect  of  hydro- 
chloric acid  (?)  and  odor  or  not  (?). 

b.  The  Properties  of  Sulphur.     Pulverize  some  sulphur  in 
the  mortar,  and  repeat  a  using  about  1  c.c.  of  sulphur  instead 
of  the  iron.     Record  the  properties  of  sulphur,  not  already 
studied  in  Exercise  3,  namely:   soluble  in  carbon  disulphide  or 
not  (?),  shape  of  crystals  (sketch  ?),  effect  of  hydrochloric  acid 
(?)  and  odor  or  not  (?). 

c.  A  Mixture.     On  a  piece  of  paper  weigh  out  3  g.  of  pul- 
verized sulphur  and  5.5  g.  of  iron  powder.      Mix  the  powders 
as  well  as  possible.     Can  the  particles  of  the  substance  still 
be  recognized  or  not?    Pass  the  magnet  underneath  the  paper 
(?).    Place  half  the  mixture  in  a  test-tube,  add  3-4  c.c.  of  car- 
bon disulphide,  shake,  and  filter  into  the  evaporating  dish. 
When  the  liquid  has  evaporated,  examine  the  residues  on  the 
paper  and  in  the  dish  (?).     Why  does  the  result  show  that  the 
material  was  a  mixture,  and  not  a  chemical  compound  [13]? 

d.  Place  the  remainder  of  the  mixture  from  c  in  a  dry  test- 
tube,  hold  the  test-tube  by  means  of  a  piece  of  folded  paper 
(Fig.  1,  Ex.  1),  and  heat  it  gently  in  the  Bunsen  flame  (?).    When 
the  test-tube  is  cold,  place  the  lower  end  in  the  mortar,  cover 
with  a  towel,  and  strike  through  the  towel  so  as  to  break  it. 
Use  the  pestle  in  this  way  until  the  material,  and  the  fragments 
of  glass  to  which  the  material  is  attached,  can  be  placed  in  another 
test-tube.    Add  2  c.c.  of  carbon  disulphide,  filter,  and  allow  the 
filtrate  to  evaporate  as  before.    Examine  the  material  on  the 
filter  to  ascertain  whether  it  is  iron  (?).     If  it  is  in  the  least 
affected  by  the  magnet,  too  little  sulphur  was  used.     Does  the 
filtrate  yield  all  the  sulphur  used  (?),  or  any  sulphur?     Place  the 
material  on  the  filter  in  a  test-tube,  add  a  few  drops  of  hydro- 
chloric acid  (odor  ?).     Did  either  iron  or  sulphur  give  this  odor? 

Record  the  properties  of  ferrous  sulphide,  namely:  color  (?), 
effect  of  hydrochloric  acid  (?)  and  odor  or  not  (?).  What  was 
the  effect  of  heating  the  mixture?  Is  the  product  an  element, 
or  a  compound,  or  a  mixture? 


8  OXYGEN  —  PRELIMINARY 

EXERCISE  6 
OXYGEN  —  PRELIMINARY 

Object:  To  learn  which  substances  yield  oxygen,  and  how  to  recognize 

.  ^. 
Apparatus:  Test-tube  (hard  glass).    Clamp.    Porcelain  crucible. 

Dropper. 
Materials:   Lead    dioxide.    Wooden    splints.     Sand.     Potassium 

chlorate.     Manganese  dioxide  (powdered).     Sodium  peroxide. 

Litmus  papers. 

a.  Place  about  1  c.c.  of  lead  dioxide  (properties  ?)  in  a  dry 
hard  glass  test-tube,  and  fasten  the  tube  in  a  vertical  position 
in  the  clamp  on  the  iron  stand.    Heat  at  first  gently  and  then 
strongly  with  the  Bunsen  flame.    Introduce  a  wooden  splint, 
glowing  at  one  end,  into  the  tube  until  the  spark  almost  reaches 
the  oxide   (?).    What  gas  is  liberated?    What  physical  and 
chemical  properties  do  you  observe  the  gas  to  have?    After 
removing  from  the  flame,  examine  the  residue  in  the  tube  (?). 
The  new  substance  is  litharge.     Name  the  variety  of  chemical 
change  illustrated  [16]. 

b.  Repeat  a,  using  1  c.c.  of  silicon  dioxide  (sand),  and  answer 
the  same  questions. 

c.  Repeat  a,  using  1  c.c.  of  potassium  chlorate  (properties  ?), 
and  answer  the  same  questions. 

d.  Repeat  a,  using  1  c.c.  of  manganese  dioxide  (properties  ?), 
having  previously  dried  this  by  warming  it  in  the  porcelain 
crucible.    Answer  the  same  questions. 

e.  Place  in  a  dry  test-tube  about  0.5  c.c.  of  sodium  peroxide. 
Using  a  dropper,  add  one  or  two  drops  of  water  to  the  peroxide 
(?).     Test  this  gas  with  a  glowing  splinter  of  wood  (?).    After- 
wards, dip  a  piece  of  red  litmus  paper  in  the  residual  liquid  (?). 
A  blue  color  indicates  the  presence  of  an  alkali  [168]  (sodium 
hydroxide). 


GLASS-WORKING  9 

EXERCISE  7 
GLASS-WORKING 

Object:  To  learn  how  to  make  simple  apparatus. 

Apparatus :  Triangular  file.    Rack.    Wing-top.    Test-tube  (hard 

glass)  and  stopper  (1-hole). 
Materials:  Glass  rod.    Glass  tubing. 

a.  Glass  Rod.  Make  a  transverse  notch  about  15  cm.  (6") 
from  the  end  of  a  glass  rod.  To  do  this,  hold  the  rod  on  the 
table  and  draw  the  edge  of  the  triangle  file  once  firmly  and 
smoothly  across  it.  Now,  break  the  rod  at  this  point  by  holding 
it  so  that  the  points  of  the  thumbs  are  together  on  the  side  oppo- 
site to  the  notch,  and  pressing  forward  with  the  thumbs  so  as  to 
bend  the  rod  away  from  the-  mark.  Cut  two  other  pieces  of  the 
same  length. 

To  remove  the  sharp,  often  jagged  edges,  hold  the  ends  of 
the  rods  in  the  Bunsen  flame,  turning  them  slowly  until  the 
edges  are  rounded  (fire-polished).  Observe  the  color  of  the 
flame  (?).  To  what  is  this  color  due  [365]?  Do  not  lay  the  hot 
rods  on  the  table,  but  balance  them  across  the  test-tube  rack  or 
on  an  iron  ring  until  cold.  Why  does  heating  the  rods  remove 
the  sharp  edges? 

6.    Glass  Tubing,  Drawing  Out.     Cut,  exactly  as  in  a,  from 
a  piece  of  glass  tubing  a  portion    —m=s=a=!X!S=—x^^ 
15  cm.  long.     Hold  the  center  of  ' 

this  piece  of  tubing  in  the  Bunsen    r  — . — ^  -  •"  ^ 

flame,  turning  it  slowly,  until  it 

becomes  soft  (Fig.  6).     Hold  and    

turn  it,  as  a  whole,  carefully,  so  ^  F       6~"" 

as  not  to  bend  or  twist  it.    When 

it  is  quite  soft,  remove  it  from  the  flame,  and  draw  the  two  ends 

slowly  apart. 

c.  Glass  Tubing,  Bending.  Fit  a  wing-top  on  the  Bunsen 
burner,  and  use  the  luminous  flame.  Hold  a  piece  of  tubing 
15  cm.  long  in  the  flame  so  that  as  long  a  portion  is  heated  as 
possible,  and  rotate  it  steadily  so  as  to  heat  all  sides  alike. 
Do  not  allow  the  tube  to  bend  or  twist.  When  the  glass  is 
quite  soft,  withdraw  the  tube  and  bend  it  to  form  a  right  angle, 
giving  an  L-tube  (Fig.  7).  The  bend  must  be  gradual  and 


10   OXYGEN  —  PREPARATION  AND  PROPERTIES 


smooth,  not  sharp  or  crumpled.    Bend  another   similar  piece 
to  form  an  obtuse  angle.     Fire-polish  the  edges  (for  this,  use 


rcr 


Right 


FlG.  7  Wrong 


FIG.  8 


the  non-luminous  flame),  but  do  not  heat  too  long, 
otherwise  the  bore  will  be  diminished. 

d.  Fit  a  stopper  into  the  hard  glass  test-tube. 
Remove  the  stopper,  and  push  the  shorter  end  of 
the  obtuse-angled  tube  through  the  hole  (Fig.  8). 
Do  not  use  force  —  moisten  the  tube  and  the  hole 
and  rotate  the  tube  while  pushing  it  gently  through 
(don't  hurry).  Allow  the  tube  to  project  not  over 
1  mm.  on  the  inside.  Replace  the  stopper  in  the 
test-tube  and  test  for  air-tightness.  To  do  this, 
place  the  end  of  the  tube  in  the  mouth,  suck  out 
some  of  the  air,  and  note  whether  the  tip  of  the 
tongue  seems  to  adhere  to  the  tube.  Remove  the 
tube  and  stopper,  and  repeat  (?).  What  caused 
the  tongue  to  adhere  in  the  first  instance? 


EXERCISE  8 
OXYGEN  —  PREPARATION  AND  PROPERTIES 

Object:  To  make  a  quantity  of  oxygen  and  to  ascertain  its  physical 
and  chemical  properties. 

Apparatus:  Mortar.  Trip  scales.  Test-tube.  Test-tube  (hard 
glass)  with  stopper  and  bent  tube  (Ex.  7  d).  Narrow  rubber 
tube  12"  long.  Clamp.  Pneumatic  trough.  3  wide-mouth 
bottles.  3  glass  plates.  Deflagrating  spoon.  Iron  wire. 

Materials:  Potassium  chlorate.  Manganese  dioxide  (powdered). 
Splints.  Asbestos  paper.  Sulphur.  Red  phosphorus.  Char- 
coal (splinters). 

a.  Pulverize  4  g.  of  potassium  chlorate.     Mix  it  on  paper 
with  2  g.  of  manganese  dioxide.     Place  about  one-tenth  of  the 


VT" 


" 


OXYGEN  —  PREPARATION  AND  PROPERTIES        1 1 

mixture  in  a  dry  test-tube,  heat  it,  and  test  the  gas  with  a 
glowing  splinter  of  wood  (?). 

b.  Place  the  remainder  of  the  mixture  in  the  hard  glass  test- 
tube  provided  with  a  stopper  and   glass  tube  (Ex.  7  d),  and 
test  for  air-tightness.     Moisten  the  end  of  a  piece  of  narrow 
rubber  tubing  (12"  long) 

and  slip  it  over  the  end 
of  the  tube.  Clamp  the 
tube  in  a  horizontal  posi- 
tion (Fig.  9).  Fill  the 
pneumatic  trough  with 
water  so  as  to  cover  the 
shelf  or  other  support. 
Fill  3  wide-mouth  bottles 
with  water,  cover  them 
with  glass  plates,  and 
invert  them,  one  on  the 
shelf,  and  the  other  two  FIG.  9 

in  the   trough.      Use  a 

small  Bunsen  flame  to  heat  the  tube  and  collect  the  first  bubbles 
of  gas  in  a  test-tube  filled  with  water  and  inverted  over  the 
exit  of  the  rubber  tube.  Test  this  gas  with  a  glowing  splinter 
(?).  What  is  this  gas,  and  where  did  it  come  from?  Now 
fill  the  bottles  one  by  one,  covering  each  when  full  with  a 
glass  plate,  and  setting  it  mouth  upwards  on  the  table.  Dur- 
ing the  operation,  regulate  the  flame  with  great  care  so  that 
the  gas  comes  off  in  a  steady,  but  not  too  rapid  stream  of 
bubbles.  If  the  gas  begins  to  come  too  fast,  move  the  flame 
promptly  to  another  part  of  the  material  and  lower  it  slightly. 
The  glass  must  not  become  hot  enough  to  tinge  the  Bunsen 
flame  yellow.  Do  not  remove  the  flame,  however,  at  any  time, 
without  first  taking  the  rubber  tube  out  of  the  water  (Why?) 
After  the  third  bottle  is  filled,  remove  the  rubber  tube  from 
the  water,  let  the  test-tube  cool  and  then  fill  it  with  water  and 
set  it  aside. 

c.  Line  the  deflagrating  spoon  with  asbestos  paper  and  place 
on  the  asbestos  a  little  sulphur.     Heat  the  sulphur  until  it 
catches  fire.     Observe  the  flame  for  a  moment  (?).     Then  lower 
the  spoon  into  one  bottle  of  oxygen  (?),  keeping  the  mouth  as 
far  as  possible  covered  with  the  glass  plate.     How  does  the  flame 
differ  from  that  in  air,  and  why?    Is  it  finally  extinguished?    If 


12  HYDROGEN  —  PRELIMINARY 

so,  why?    Cautiously  note  the  odor  (?).    Name  the  product  (?) 
and  state  its  physical  properties  (?). 

d.  Reline  the  spoon  with  asbestos  and  place  on  it  a  little  red 
phosphorus.     Set  fire  to  the  latter,  observe  the  flame  (?)  and 
lower  the  spoon  into  the  second  bottle  as  before  (?).     Name 
the  product  (?)  and  state  its  physical  properties  (?). 

Before  putting  the  spoon  away,  heat  both  it  and  the  asbestos 
strongly  in  the  Bunsen  flame  to  burn  up  all  the  phosphorus. 

e.  Wrap  the  end  of  a  piece  of  wire  round  a  splinter  of  char- 
coal, set  fire  to  the  latter,  and  lower  it  into  the  third  bottle  as 
before  (?).    How  does  its  combustion  compare  with  that  in  air? 
Name  the  product  (?)  and  state  its  physical  properties  (?). 

/.  Record  the  physical  properties  of  oxygen:  color  (?),  odor 
(?),  solubility  in  water  (?).  Record  the  chemical  properties: 
glowing  splint  (?),  sulphur  (?),  phosphorus  (?),  charcoal  (?). 
What  is  the  difference  between  a  chemical  and  a  physical 
property?* 

EXERCISE  9 

HYDROGEN  —  PRELIMINARY 

(Interaction  of  metals  with  acids  and  water) 

Object:  To  learn  various  ways  of  obtaining  hydrogen  and  to  compare 
them. 

Apparatus:  12  test-tubes.  Graduated  cylinder.  Evaporating 
dish.  Large  beaker. 

Materials:  Iron  (nails).  Zinc  (gran.).  Tin  (gran.)  Copper 
(shavings).  Aluminium  (wire).  Magnesium  (ribbon).  Hydro- 
chloric acid  (cone.).  Zinc  (dust).  Sulphuric  acid  (dil.). 
Acetic  acid.  Calcium.** 

a.  Place  in  separate  test-tubes  a  few  small  pieces  of  each 
of  the  metals,  iron  (nails),  zinc  (granulated),  tin  (granulated), 
copper  (shavings),  aluminium  (wire),  magnesium  (ribbon). 
Pour  into  the  graduated  cylinder  20  c.c.  of  pure  concentrated 

*  Exercise  14  (except  /)  may  be  introduced  here,  if  desired. 
**  Calcium  (metal)  is  most  easily  broken  into  small  pieces  by  fixing 
it  in  a  vise  and  using  a  chisel  and  hammer. 


' 


t 


HYDROGEN  —  PRELIMINARY  13 

hydrochloric  acid,  add  an  equal  volume  of  water,  and  mix. 
Add  5  c.c.  of  this  diluted  acid  to  the  contents  of  each  tube. 

Observe  each  case  critically,  and  tabulate  the  results.  Is 
there  bubbling?  If  not,  then  warm  gently  (?).  If  the  eye 
detects  the  formation  of  a  gas  or  vapor,  smell  the  contents  of 
the  tube  (?).  For  comparison,  take  5  c.c.  of  the  acid  by  itself 
in  a  test-tube,  smell  it  (?),  warm  and  smell  again  (?).  If  heat- 
ing seems  to  produce  a  gas,  remember  that  it  may  be  the  acid 
boiling,  or  steam  and  not  hydrogen.  The  formation  of  hydrogen 
may  be  inferred  from  continued  bubbling  when  heat  is  not  being 
furnished,  and  may  be  proved  by  the  slight  explosion  which 
follows  when  a  light  is  brought  to  the  mouth  of  the  tube.  If 
the  gas  is  coming  slowly,  hinder  its  escape  into  the  air  by  partially 
closing  the  mouth  of  the  tube  and  let  it  accumulate  before  apply- 
ing the  light. 

Number  the  metals  in  your  notes  in  the  order  of  their  ap- 
parent activity  (most  active  =  No.  1).  Do  the  bubbles  appear 
on  the  side  of  the  glass  tube  or  on  the  metal?  Why  do  they 
appear  on  one  and  not  on  the  other?  Record  the  properties 
of  hydrogen  you  have  observed:  Gas,  liquid  or  solid  (?),  soluble 
in  water  or  not  (?),  colored  (?),  odor  or  not  (?),  unites  with 
oxygen  from  the  air  or  not  (?)  and  if  so  when  cold  or  hot  (?). 

6.  After  the  action  has  ceased,  filter  any  one  of  the  solutions 
and  evaporate  (Ex.  10  /)  1  c.c.  of  it  to  dryness  [HOOD]  (?). 
What  is  the  product?  Record  the  action  in  each  case  in  the 
form  of  a  condensed  statement  [63]. 

c.  Add  some  zinc  dust  to  the  remaining  5  c.c.  of  the  acid  (?). 
To  what  is  the  difference,  if  any,  between  the  apparent  activity 
of  zinc  dust  and  granulated  zinc  due? 

d.  The  same  metals  displace  hydrogen  from  all  acids.     To 
illustrate,  plA.ce  a  few  pieces  of  zinc  (gran.)  in  each  of  two  test- 
tubes  and  add  to  one  5  c.c.  of  dilute  sulphuric  acid  (?)  and  to  the 
other  5  c.c.  of  acetic  acid  (?). 

e.  Fill  a  test-tube  with  water,  and  invert  it  in  the  large  beaker 
half  filled  with  water.     Place  a  small  piece  of  calcium  in  the 
water  and  hold  the  test-tube  over  it  (?).    After  the  action  has 

apply  a  light  to  the  gas  in  the  tube  (?).    Examine 
f  water  in  the  beaker  (?)  and  test  it  with  red  litmus  paper  (?). 


14    HYDROGEN  —  PREPARATION  AND  PROPERTIES 

EXERCISE   10 
HYDROGEN  —  PREPARATION  AND  PROPERTIES 

Object:   To  prepare  a  quantity  oj  hydrogen  and  observe  its  physical 

and  chemical  properties. 
Apparatus:   90  c.c.  gas-generating  bottle  with  2-hole  stopper  and 

thistle-tube.     Glass  tubing.     12"  narrow  rubber  tube.    Trough. 

Trip  scales.     Test-tubes.     2  wide-mouth  bottles  and  2  glass 

plates.     Watch  glass.     Beaker.     Wire  gauze.     Taper. 
Materials:   Zinc  (gran.).    Sulphuric  acid  (cone.).    Cupric  oxide. 

a.  Fit  the  90  c.c.  gas-generating  bottle  with  a  2-hole  stopper, 
a  thistle-tube,  and  an  L-tube  (Fig.  10).    Slip  the  narrow  rubber 

tube  over  the  end  of  the  last.  Place  in  the  bottle 
about  20  g.  of  zinc  (gran.).  Test  the  apparatus  to 
see  whether  it  is  air-tight.  To  do  this,  pour  into  the 
bottle  through  the  thistle-tube  enough  water  to  cover 
the  zinc.  The  lower  end  of  the  thistle-tube  must 
also  be  under  the  water.  Now  blow  through  the 
rubber  tube  a  little  air,  so  as  to  force  the  water  up 
the  stem  of  the  thistle-tube,  and  immediately  com- 

press  the  rubber  tube   with  the    thumb   and  fore- 

FIG.  10     finger-    If  "the  water  does  not  remain   stationary, 
but  gradually  falls,  there  is  a  leak  which  must  be 
remedied  [Instructor]. 

Add  concentrated  sulphuric  acid  slowly  through  the  thistle- 
tube  until  brisk  bubbling  sets  in.  Do  not  add  more  than  one- 
fourth  of  the  volume  of  the  water  already  in  the  bottle.  Place 
ijie  end  of  the  rubber  tube  in  the  trough.  Collect  a  test-tube 
full  of  the  gas.  Close  the  tube  with  the  thumb  and  carry  it 
mouth  downwards  to  a  distant  flame.  Remove  the  thumb 
and,  still  holding  the  tube  mouth  downwards,  set  fire  to  the  gas. 
Repeat  this  test  until  a  sample  is  obtained  which  burns  quietly. 
Why  does  it  not  do  so  at  first?  Do  not  at  any  tune  attempt  to 
light  the  gas  at  the  exit  tube. 

b.  Collect  over  water  two  bottles  of  the  gas.    Cover  the  : 
with  a  glass  plate  and  set  it  mouth  downwards  on  the 
Light  a  taper,  raise  this  bottle  (still  mouth  downwards),  ic 
the  burning  taper  (?)  almost  to  the  bottom  of  the  bottle 
and  then  withdraw  it  slowly  (?).    What  happens  to  the  Jas? 


WATER  —  PHYSICAL  PROPERTIES  15 

What  happens  to  the  taper  on  insertion  and  on  withdrawal? 
Explain. 

c.  Set  the  other  bottle  mouth  upwards  on  the  table  and  leave 
it  open  for  one  minute.     Then  bring  a  lighted  taper  to  the 
mouth  (?).    Explain. 

d.  Fill  a  test-tube  over  water  with  the  gas.     Bring  this  tube, 
mouth  downwards,  mouth  to  mouth  with  a  test-tube  filled  with 
air,  and  keep  them  in  this  position  for  3  minutes.     Then  apply 
a  light  first  to  the  lower  (?)  and  then  to  the  upper  tube  (?). 
What  fact  about  the  molecules  of  gases  is  shown  by  this  experi- 
ment? 

e.  Place  0.5  c.c.  of  cupric  oxide  in  the  bottom  of  a  dry  test- 
tube  and  fasten  the  latter  in  a  horizontal  position  in  the  clamp 
on  the  iron  stand.     Insert  a  straight  piece  of  glass  tubing  (ends 
fire-polished)  into  the  rubber  delivery  tube  and  introduce  this 
tube  into  the  test-tube  until  the  end  touches  the  cupric  oxide. 
Wait  3  minutes,  to  permit  the  air  to  be  replaced  by  hydrogen. 
If  the  hydrogen  is  being  given  off  too  slowly,  pour  a  little  more 
sulphuric  acid  into  the  thistle-tube.     Now  heat  the  cupric  oxide 
with  a  Bunsen  flame.     Note  any  change  in  the  cupric  oxide  (?) 
and  anything  appearing  in  or  on  the  cool  part  of  the  tube  (?). 

Make  a  condensed  statement  of  this  action.  What  kind  of 
chemical  action  is  this  [57]? 

/.  Place  3  drops  of  the  liquid  from  the  gas-generating  bottle 
on  a  watch  glass.  Place  the  watch  glass  on  a  beaker  half  filled 
with  water,  set  the  beaker  on  the  wire  gauze  and  boil  the  water. 
If  the  water  in  the  beaker  runs  too  low,  because  of  evaporation, 
the  vessel  may  crack.  Add  more  hot  water,  if  necessary.  What 
is  the  solid  left  on  the  watch-glass  by  evaporation? 

g.  Record  the  observed  physical  properties  of  hydrogen, 
namely:  color  (?),  odor  (?),  density  compared  with  air  (?); 
also  two  chemical  properties  observed  in  b  (?)  and  one  in  e  (?) . 

EXERCISE  11 
WATER  —  PnrateAL  PROPERTIES 

Object:   To  learn  how  to  purify  water,  and  how  to  find  out  whether 

it  contains  non-volatile  impurities. 
Apparatus:  Flask.    Glass  tubing.    Test-tubes.    Beakers.    Clamp. 

Wire  gauze.    Watch-glass. 


16  WATER  — PHYSICAL  PROPERTIES 

Materials:  Marble  (chips).  Potassium  permanganate  (sol.). 
Phenolphthalein  (sol.  in  alcohol,  1:500).  Ammonium  hy- 
droxide (sol.). 

a.  Put  on  a  clean  watch-glass  3-4  drops  of  distilled  water, 
place  the  watch-glass  on  a  100  c.c.  beaker  half  filled  with  water, 
and  set  the  beaker  on  the  wire  gauze  and  boil  (see  directions  in 
Ex.  10  /).  Put  on  a  second  clean  watch-glass  3-4  drops  of  tap- 
water  and  evaporate  in  the  same  way.  Compare  the  two  watch- 
glasses  when  dry  (?).  Do  the  specimens  of  water  contain  any 
non-volatile  impurities? 

6.  Distillation.  Bend  a  piece  of  glass  tubing  twice  at  right 
angles  and  fire-polish  the  ends.  Connect  with  it,  by  means  of 
a  short  piece  of  rubber  tubing,  a  straight  tube 
about  30  cm.  long.  Set  up  a  flask  and  a  test- 
tube  immersed  in  cold  water  in  the  300  c.c. 
beaker  as  in  Fig.  11.  Place  in  the  flask  about 
100  c.c.  of  water,  some  marble  chips  (to 
prevent  " bumping"),  and  a  few  drops  of 
potassium  permanganate  solution.  Boil  the 
water  and  examine  the  distillate  (in  the  test- 


FIG.  11          tube). 

.  In  what  way  has  the  water  been  purified 
by  the  distillation?  Is  potassium  permanganate  volatile  under 
these  conditions?  If  it  had  been,  would  distillation  have  puri- 
fied the  water? 

c.  Add  one  drop  of  phenolphthalein  solution  to  some  tap- 
water  (?).    Add  one  drop  of  ammonium  hydroxide  solution  to 
some  tap-water,  and  then  add  one  drop  of  phenolphthalein  (?) . 

d.  Using  a  glass  rod,  add  a  single  drop  of  ammonium  hy- 
droxide solution  to  100  c.c.  of  tap-water.    Clean  and  use  the 
same  apparatus  as  in  b,  place  this  water  in  the  flask,  and  distil  as 
before.    In  each  of  six  clean  test-tubes  place,  from  a  glass  rod, 
one  drop  of  phenolphthalein  solution,  and  use  these  test-tubes 
one  after  another  to  catch  the  distillate.    Change  the  test-tube 
when  10  c.c.  of  liquid  has  come  over  until  the  six  have  been  used. 
While  changing,  remove  the  flame  and  uncork  the  flask  each  time. 
If  the  water  in  the  beaker  becomes  warm,  change  it  for  cold 
water. 

What  evidence  is  there  that  ammonia  passes  over  with  the 
steam?    Which  portion  of  the  distillate  contained  the  most 


HYDRATES  17 

ammonia  and  which  the  least?  Cool  the  residue  in  the  flask  in 
running  water,  pour  10  c.c.  of  it  into  a  clean  test-tube  and  add 
one  drop  of  phenolphthalein  (?).  Can  water  be  purified  from 
a  volatile  impurity? 

e.  Name  the  common  states  in  which  water  exists  (?).    How 
many  states  of  water  are  known  altogether  [64]? 

EXERCISE  12 
HYDRATES 

Object:  To  team  how  to  find  out  whether  a  substance  is  a  hydrate  or 
not. 

Apparatus:  Watch-glass.    Test-tubes.    Clamp.    Mortar. 

Materials:  Washing  soda.  Potassium  chlorate.  Aluminium  sul- 
phate. Potassium  sulphate.  Barium  chloride.  Gypsum  (frag- 
ments). Cupric  sulphate. 

a.  Place  a  clear  crystal  of  washing  soda  (sodium  carbonate) 
on  a  watch-glass  and  set  it  aside.    At  the  end  of  the  period, 
examine  it  and  record  any  changes  you  observe  (?). 

b.  Place  a  clear  crystal  of  washing  soda  in  a  test-tube  and 
heat  the  crystal  gently  (?).    What  condenses  on  the  walls  of  the 
tube?    Explain  the  result  of  a  [68]. 

c.  Place  in  different  test-tubes  about  1  c.c.  each  of  potas- 
sium chlorate,  aluminium  sulphate,  potassium  sulphate,  barium 
chloride,  and  gypsum  (calcium  sulphate).     Clamp  one  tube  in  a 
horizontal  position,  to  prevent  any  condensed  water  from  run- 
ning back  and  causing  the  tube  to  crack,  and  heat  the  substance 
with  the  tip  of  a  small  flame  until  no  further  change  occurs  (?) . 
Repeat  with  each  tube.    Record  the  results  in  tabular  form  as 
follows: 

SUBSTANCE  WHAT  AMOUNT  OF  APPEARANCE  SUBSTANCE  WAS 
HEATED  CHANGE  CONDENSED  OF  FINAL  A  HYDRATE 

WATER  RESIDUE  OR  NOT 

The  amount  of  the  water  condensed  may  be  "great,"  "small," 
or  "a  trace."  Remember  that  even  an  anhydrous  substance 
may  contain  a  little  water,  as  an  impurity.  Hence,  a  substance 
is  not  to  be  classed  as  a  hydrate  (last  column)  unless  the  libera- 
tion of  water  is  distinctly  evident. 


18      MEASUREMENT  OF  WATER  OF  HYDRATION 

Are  all  crystalline  substances  hydrates?  Illustrate.  Make 
a  condensed  statement  of  the  change  in  each  case  in  which  water 
was  given  off. 

d.  Take  about  1  c.c.  of  copper  sulphate  crystals.  Note  their 
color  (?).  Pulverize  them  finely  in  the  mortar  and  note  the 
color  again  (?).  Explain. 

Place  the  powder  in  a  dry  test-tube,  clamp  the  latter  in  a 
horizontal  position,  heat  the  substance  as  in  c  and  tabulate  the 
results  as  before. 

Leave  the  tube  in  the  clamp  until  it  is  cold,  and  then  set  it 
upright  (?).  If  there  is  not  enough  water  condensed  to  permit 
some  to  run  down  to  the  solid  residue,  add  two  drops  (?).  Note 
the  color.  What  substance  is  formed? 

Make  a  condensed  statement,  showing  the  action  to  be  re- 
versible [69].  Record  its  color  under  the  name  of  each  substance. 

EXERCISE   13 

QUANTITATIVE   MEASUREMENT   OF  WATER  OF  HYDRATION 

Object:  To  find  the  per  cent  of  the  elements  of  water  in  gypsum 

(hydrated  calcium  sulphate)  or  in  barium  chloride. 
Apparatus:  Porcelain  crucible.    Balance.    Pipe-stem  triangle. 
Materials:  Gypsum  (powdered  crystals).     Barium  chloride. 

a.  Clean  and  dry  the  porcelain  crucible  and  weight  it  to 
the  nearest  centigram  (0.01  g.),  counting  the  weights  as  in  3  a. 
Then  place  in  it  about  2  g.  of  pulverized  gypsum  (do  not  try  to 
take  this  exact  amount)  and  weigh  again  as  before.  Record  the 
weights  in  tabular  form  as  shown  below. 

Support  the  crucible  (open)  on  the  pipe-stem  triangle,  placed 
on  the  ring  of  the  iron  stand,  so  that  the  bottom  of  the  crucible 
is  a  short  distance  above  the  inner  cone  of  the  Bunsen  flame. 
Lower  the  flame  and  heat  at  first  very  gently  to  avoid  loss  of  any 
particles  by  sudden  splitting  of  the  crystals.  Later  use  the  full 
flame. 

After  15  minutes'  heating,  allow  the  crucible  to  cool  and  weigh 
to  the  nearest  centigram.  Replace  the  crucible  on  the  triangle, 
heat  again  for  5  minutes,  allow  to  cool  and  weigh  again.  If  the 
weight  is  less  than  before,  heat  once  more,  and  repeat  until  two 
successive  weighings  are  identical,  i.e.,  "heat  to  constant  weight." 


WEIGHT  OF  22.4  LITERS  OF  OXYGEN  19 

What  does  this  constant  weight  show  about  the  water  of  hy- 
dration? 

Wt.  of  crucible  +  gypsum                                                         g. 
Wt.  of  crucible  empty  g. 

Wt.  of  gypsum  taken  g. 

Wt.  after  first  heating  g. 

Wt.  of  crucible  +  gypsum  g. 

Wt.  after  last  heating  ^ g. 

Wt.  of  water  of  hydration  g. 

wt.  of  water  X  100     0 

Per  cent  of  water  = — ; =  7 

wt.  of  gypsum 

When  the  percentages  obtained  by  all  who  have  done  the 
experiment  are  compared,  what  law  of  chemistry  is  found  to  be 
illustrated?  Record  the  average  of  the  values  found  by  all  for 
the  percentage. 

b.  Some  members  of  the  class  may  be  directed  to  use  barium 
chloride,  following  otherwise  all  the  directions  given  for  gypsum. 

EXERCISE  14 
WEIGHT  OF  22.4  LITERS  OF  OXYGEN 

Object:  To  learn  the  weight  of  a  measurable  volume  of  oxygen.  Also 
to  make  the  necessary  corrections  and  calculate  the  density  and 
molecular  weight  of  this,  or  of  any  other  gas  (quantitative). 

Apparatus:  Trip  scales.  Porcelain  crucible.  Iron  wire.  Hard 
glass  test-tube  with  1-hole  stopper,  bent  tube  and  narrow 
rubber  tubing.  2-liter  bottle.  Trough.  Thermometer  (one 
for  class).  Barometer.  Glass  plate  or  cork.  Balance.  500  c.c. 
graduated  cylinder  (1  for  10  pupils). 

Materials:  Manganese  dioxide  (powdered,  dried).  Potassium 
chlorate  (chemically  pure,  powdered,  dry). 

a.  Place  6  g.  of  pulverized  manganese  dioxide  in  the  por- 
celain crucible  (uncovered)  and  heat  it  with  the  full  Bunsen 
flame  for  5-6  minutes.  During  this  time,  stir  it  occasionally 
with  an  iron  wire. 

While  this  is  going  on,  insert  an  obtuse-angled  tube  in  a  one- 
hole  rubber  stopper  which  fits  the  hard  glass  test-tube  (as  in 


20  WEIGHT  OF  22.4  LITERS  OF  OXYGEN 

Fig.  8,  Ex.  7  d).  Fill  a  2-liter  bottle  with  water,  invert  it  in  the 
pneumatic  trough,  and  arrange  the  apparatus  as  in  Fig.  9,  Ex.  8. 
Take  7  g.  of  dry,  pulverized  potassium  chlorate  and,  when 
the  manganese  dioxide  has  cooled,  mix  the  two  substances 
thoroughly  on  a  sheet  of  paper.  Place  the  mixture  in  the  hard 
glass  test-tube.  Weigh  on  the  balance  the  test-tube  and  con- 
tents to  the  nearest  centigram  and  record  the  result  according 
to  the  table  below  (?).  Replace  the  stopper  in  the  test-tube, 
and  test  for  airtightness  (see  Ex.  7  d). 

b.  Heat  the  contents  of  the  test-tube,  beginning  at  the  end 
next  to  the  stopper,  and  collect  all  the  gas  in  the  bottle.    Regu- 
late the  heating  so  that  you  can  at  all  times  count  the  bubbles. 
Continue   heating   until   gas  ceases  to  come  off,  and  then  re- 
move the  rubber  tube  from  the  water  and  allow  the  test-tube 
to  cool. 

Lower  the  bottle  of  gas  in  the  pan  until,  when  the  eye  is  on 
a  level  with  the  water,  the  latter  is  seen  to  be  at  the  same  height 
inside  and  outside.  To  accomplish  this  and  the  next  operation, 
it  may  be  necessary  to  incline  the  bottle.  While  the  bottle  is 
in  this  position,  close  it  with  a  cork  or  glass  plate  and  set  it  mouth 
upwards  upon  the  table.  Read  and  record  the  temperature  of 
the  water  (?)  and  also  the  barometric  pressure  (?).  If,  at  this 
point,  there  is  not  time  to  complete  the  experiment,  the  test-tube 
may  be  corked  tightly  and  put  away  (upright)  along  with  the 
2-liter  bottle  and  its  contents. 

c.  Weigh  on  the  balance  the  test-tube  and  contents,  and 
record  the  weight  (?).    To  measure  the  volume  of  gas  collected 
in  the  bottle,  fill  the  500  c.c.  graduated  cylinder  to  the  top  of  the 
graduation,  note  down  the  volume  of  water,  and  pour  the  latter 
into  the  bottle.     Repeat  until  the  bottle  is  filled  level  with  the 
mouth,  and  record  in  the  table  the  total  volume  of  water  used. 

Wt.  of  test-tube  and  contents  before  heating  g. 

Wt.  of  test-tube  and  contents  after  heating  ^ 

Wt.  of  Oxygen  g. 

Volume  of  Oxygen  c.c. 

Temperature  C. 

Barometric  Pressure  mm. 

Tension  of  aqueous  vapor  [658]  mm 

Barometric  pressure,  corrected  [471  mm. 


ATOMIC  AND  MOLECULAR  WEIGHTS 


21 


d.  Reduce  the  observed  volume  of  oxygen  from  the  observed 
temperature  and  pressure  to  0°  and  760  mm.  [45-7]. 

e.  From  this  reduced  volume,  and  the  weight,  calculate  the 
weight  of  1  c.  c.  (the  density)  of  oxygen. 

Wt.  of  oxygen 

— ] — TT^ i  ~n~       -  =  x  =  wt.  of  1  c.c.  =  density. 

vol.  at  0°  and  760  mm. 

/.  Calculate  also  the  weight  of  22.4  liters   (the  molecular 
weight)  of  oxygen  [75]: 

wt.  of  1  c.c.  X  22400  =  x  =  wt.  of  22.4 1.  =  mol.  wt. 

Compare  the  molecular  weight  found  with  the  atomic  weight 
of  oxygen  (?).  How  many  atoms  of  oxygen  are  there  in  one 
molecule  of  the  element? 


EXERCISE  15 
ATOMIC  AND  MOLECULAR  WEIGHTS 

Object:   To  find  atomic  weights  from  data  given.     Also  to  become 
familiar  with  the  relations  between  density  and  molecular  weight 

a.  The  corrected  weights  of  one  G.M.V.  (22.4  liters  at  0°  and 
760  mm.)  of  several  compounds  of  carbon  are  as  follows : 


Wt.  22.4  1. 

Wt.  carb. 

Wt.  hyd. 

Wt.  ox. 

Formula 

Carbon  monoxide  

28.005. 

12.005 

16 

Carbon  dioxide        .  . 

44  005 

12.005 

32 

Methane         

16.037 

12.005 

4.032 

Ethylene  

28.042 

24.010 

4.032 

Glycerine  (vapor)  .... 

92.079 

36.015 

8.064 

48 

What  value  should  you  select  for  the  atomic  weight  of  carbon 
[79]?  Assuming  the  formulae  and  atomic  weights  to  be,  for 
hydrogen  H  =  1.008,  for  oxygen  0  =  16,  and  for  carbon  C  =  ?, 
write  the  formulae  for  each  of  the  five  compounds. 

b.  The  density  (wt.  of  1  c.c.  at  0°  and  760  mm.)  of  ethylene 
chloride  is  0.00433  g.,  what  is  the  molecular  weight  [75]? 

c.  Using  the  weights  in  22.4  1.  given  above,  find  the  weight 
of  1  c.c.  (the  densities)  of  methane  and  carbon  dioxide. 


COMPOSITION  OF  NICKEL  SULPHIDE 

d.  How  do  the  densities  of  the  five  substances  mentioned  in 
a  compare  with  that  of  air  [86]  ? 

e.  The  weight  of  zinc  combining  with  35.46  g.  (one  atomic 
weight)  of  chlorine  is  32.68  g.     The  specific  heat  of  zinc  (metal) 
is  0.0936.    What  is  the  atomic  weight  of  zinc  [87]  ? 

EXERCISE  16 

COMPOSITION  AND  FORMULA  OF  NICKEL  SULPHIDE 

Object:   To  find  the  composition  and  formula  of  nickel  sulphide 

(quantitative) . 
Apparatus:  Porcelain  crucible  and  cover.    Balance.     Pipe-stem 

triangle. 
Materials:  Nickel  powder  (reduced).    Flowers  of  sulphur. 

a.  Weigh  the  crucible  (without  cover)  to  the  nearest  centi- 
gram, counting  the  weights  as  in  3  a.  Place  about  2  g.  of  re- 
duced nickel  (do  not  attempt  to  take  this  amount,  exactly) 
in  the  crucible  and  weigh  again.  Put  about  2  g.  of  sulphur  in 
the  crucible  and  place  the  latter  on  the  pipe-stem  triangle.  Set 
the  cover  on  the  crucible,  and  heat  gently  so  long  as  sulphur 
vapor  burns  [HOOD]  at  the  chink  between  the  crucible  and 
cover.  Heat  strongly  for  1-2  minutes.  Then  hold  the  flame 
against  the  upper  portion  of  the  crucible,  so  that  every  part 
receives  a  thorough  heating.  Allow  the  crucible  to  cool.  When 
it  is  cold  (not  before)  remove  the  cover  and  weigh.  Tabulate 
the  results  as  follows: 

Wt.  of  crucible  +  nickel  g. 

Wt.  of  crucible  empty  £  t  *|      §»: 

Wt.  of  nickel  taken  g. 

Wt.  of  crucible  +  nickel  sulphide  g. 

Wt.  of  crucible  +  nickel  g. 


Wt.  of  sulphur  combined  g. 

Wt.  of  crucible  +  nickel  sulphide  g. 

Wt.  of  crucible  empty  g. 

Wt.  of  nickel  sulphide  g. 


COMPOSITION  OF  OXIDE  OF  TIN  23 

b.  Calculate  the  percentage  composition: 

wt.  of  sulphur  X  100       9 


Per  cent  sulphur  = 


wt.  of  nickel  sulphide 


wt.  of  nickel  X  100        0 
Per  cent  nickel  =  — —     .       —       ,    =  r 
wt.  of  nickel  sulphide 

c.  Find  the  formula  of  nickel  sulphide  [99].     To  do  this, 
first  obtain  the  atomic  weights  of  nickel  and  sulphur  from  the 
table. 

Wt.  of  sulphur  -T-  at.  wt.  of  sulphur  =  ?  (factor  1). 
Wt.  of  nickel  -r-  at.  wt.  of  nickel  =  ?  (factor  2). 

The  combining  proportion  of  sulphur  to  nickel  found  in  the 
experiment  is  therefore: 

At.  wt.  sulphur  X  factor  1  _  S  X  factor  1 
At.  wt.  nickel  X  factor  2       Ni  X  factor  2 

Divide  above  and  below  by  factor  1.    What  is  the  formula? 

d.  Make  the  equation  for  the  union  of  sulphur  and  nickel  to 
form  nickel  sulphide. 


EXERCISE  17 
COMPOSITION  AND  FORMULA  OF  OXIDE  OP  TIN 

Object:   To  find  the  proportions  of  tin  and  oxygen  in  oxide  of  tin 

(stannic  oxide)  and  the  formula  of  the  latter  (quantitative) . 
Apparatus:   Porcelain  crucible.     Balance.     Pipe-stem  triangle. 
Materials:  Tin  foil  (free  from  lead).     Nitric  acid  (cone.). 

a.  Weigh  the  crucible  (without  cover)  (?).  Place  in  it  about 
1  g.  of  tin  foil  (do  not  try  to  take  exactly  1  g.)  and  weigh  again 
(?).  Record  the  weights  in  tabular  form  (see  below).  Place 
the  crucible  on  the  pipe-stem  triangle  and  add  5  c.c.  of  concen- 
trated nitric  acid.  In  doing  this,  pour  the  acid  over  every  part 
of  the  metal.  Hold  the  burner  in  the  hand  and  warm  the  cru- 
cible with  a  very  small  flame,  stopping  for  a  moment  if  there  is 
a  tendency  for  any  particles  to  be  spattered  out  of  the  vessel. 
When  the  contents  are  dry,  use  a  larger  flame  and  heat  for  ten 
minutes.  Weigh  when  cold  (?). 


24  SOLVENTS  AND  SOLUBILITY 

The  nitric  acid  oxidizes  the  tin.    A  brown  gas,  nitrogen 
tetroxide,  and  water  are  given  off  during  the  process. 

Wt.  of  crucible  +  tin  g. 

Weight  of  crucible,  empty  _  ^ 

Wt.  of  tin  taken  g. 

Wt.  of  crucible  +  oxide  of  tin  g. 
Wt.  of  crucible  +  tin 


Wt.  of  oxygen  g. 

Wt.  of  crucible  +  oxide  of  tin  g. 

Wt.  of  crucible,  empty  _  g. 

Wt.  of  oxide  of  tin  g. 

6.  Calculate  the  percentage  composition  of  the  oxide  of  tin. 

c.  Find  the  atomic  weight  of  tin  in  the  table  and  calculate  the 
formula  of  the  oxide. 

d.  From  the  data  obtained  in  Ex.  13,  calculate  the  formula 
of  the  hydrate.    Proceed  as  follows: 

Wt.  of  water  -f-  Formula  wt.  of  water  (H20  =  2  X  1.008  + 
16  =  18.016)  =  x. 

Wt.  of  residue  •*-  Formula  wt.  of  residue  (CaS04  =  40.07  + 
32.06  +  4  X  16  =  136.13)  =  y. 

wt.  of  water  18.016  X  x  =  s(H20) 

wt.  of  calcium  sulphate"  136.13  X  y  ~2/(CaS04)' 

Divide  both  x  and  y  by  y.  This  will  give  the  smallest  whole 
numbers  which  are  in  the  same  ratio.  Then  substitute  these 
whole  numbers  for  x  and  y  in  2/CaS04,zH2O. 

In  13  6,  the  formula  is  2/BaCl2,zH20,  and  the  values  of  x  and  y 
are  found  in  the  same  way. 

EXERCISE  18 
SOLVENTS  AND  SOLUBILITY 
(With  practical  applications) 

Object:  To  find  out  how  to  hasten  the  process  of  solution,  and  the 
difference  between  solution  and  suspension.  To  learn  what  solvents 
dissolve  certain  common  materials. 


SOLVENTS  AND  SOLUBILITY  25 

Apparatus:  Test-tubes  and  rack.  Corks  to  fit.  Mortar.  Gradu- 
ated cylinder.  Glass  rod. 

Materials:  Cupric  sulphate  (hydrate).  Filter  paper.  Potassium 
permanganate.  Powered  rosin.  Alcohol  (95%  denatured). 
Fat  (or  lard).  Carbon  tetrachloride.  Paraffin.  Gasoline  (or 
benzene) . 

a.  A  mass  dissolves  at  its  surface  only.    The  larger  the  total 
surface,  the  faster  it  dissolves. 

Take  two  large  crystals  of  cupric  sulphate  of  equal  size  and 
yjt  of  such  size  that  each  can  be  slipped  into  a  test-tube.  Pro- 
vide two  dry  test-tubes  with  corks  to  fit.  Pulverize  one  of  the 
crystals  very  finely  in  the  mortar,  so  that  no  large  particles  are 
visible.  Place  the  powder  in  one  test-tube  and  the  crystal  in  the 
other.  Add  from  the  graduated  cylinder  20  c.c.  of  water  to  each. 
Cork  the  tubes  quickly,  note  the  time  on  a  watch  (?),  and  shake 
the  tubes  gently.  When  the  powder  has  all  dissolved,  note  the 
time  again  (?).  Estimate  the  fraction  of  the  original  crystal 
which  remains  in  the  other  tube,  then  continue  shaking  it  until 
it  also  has  dissolved,  and  note  the  time  again  (?).  Compare  the 
total  times  required  to  dissolve  each  (?).  Why  does  pulveriza- 
tion make  this  difference  in  the  rate  of  solution?  To  save  time, 
in  what  form  should  you  use  a  substance  to  be  dissolved? 

b.  Take  again  two  nearly  equal-sized,  but  smaller  crystals  of 
cupric  sulphate.     Fill  two  test-tubes  with  water. 

Put  one  of  the  crystals  into  one  of  the  tubes. 
Drop  the  other  crystal  into  the  second  tube  (Fig. 
12),  so  that  it  is  covered  by  the  water,  but  rests 
on  a  narrow  strip  of  ordinary  paper.  Set  both 
tubes  upright  in  the  rack.  How  long  does  each 
crystal  take  to  dissolve? 

If  you  had  to  dissolve  a  large  amount  of  ma- 
terial quickly,  with  the  least  expenditure  of  effort, 
how  should  you  proceed  (in  answering,  take  the 
results  of  both  a  and  b  into  account)?  While  the 
tubes  are  standing,  go  on  with  c,  d  and  e.  -p 

c.  On  to  a  strip  of  paper  dipping  under  water 

(Fig.  12),  drop  a  crystal  of  potassium  permanganate  (?).    Ex- 
plain (?). 

d.  Place  1  c.c.  of  powdered  rosin  in  each  of  two  dry  test-tubes. 
Add  to  one  5  c.c.  of  alcohol  and  to  the  other  5  c.c.  of  water  and 
shake  both  (?). 


26  SOLUBILITY  AND  TEMPERATURE 

Pour  the  alcoholic  liquid  into  a  large  beaker  full  of  water. 
In  what  ways  is  a  suspension  like  a  solution  (?)  and  how  does 
it  differ? 

Should  you  remove  rosin  (or  varnish  or  a  similar  gum)  from 
clothing  with  water?  With  alcohol? 

e.  Place  a  small  piece  of  lard,  half  the  size  of  a  pea,  in  each 
of  two  test-tubes.  Add  2  c.c.  of  water  to  one  and  2  c.c.  of  car- 
bon tetrachloride  to  the  other  and  shake  (?).  How  should  you 
remove  grease  from  clothing?  (In  removing  a  grease-spot, 
place  the  part  flat  on  a  piece  of  blotting  paper,  to  absorb  the 
solution,  and  rub  the  spot  with  a  rag  dipped  in  the  solvent.) 

/.  Use  small  pieces  of  solid  paraffin  as  in  e,  employing  water 
and  gasoline  or  benzene  as  solvents. 

g.  Take  10  c.c.  of  water  in  each  of  three  test-tubes.  To  one 
add  a  single  drop  of  alcohol  and  shake.  Does  the  alcohol  dis- 
solve? Add  more  alcohol,  a  few  drops  at  a  time,  until  about 
5  c.c.  have  been  added.  Has  the  amount  added  yet  become 
greater  than  the  water  can  dissolve? 

To  the  second  tube  add  carbon  tetrachloride  (or  carbon  di- 
sulphide)  in  the  same  way,  and  answer  the  same  questions  (?) . 

To  the  third  add  gasoline  (or  benzene)  in  the  same  way,  and 
answer  the  same  questions. 

If  you  had  a  mixture  of  sugar  (which  is  soluble  in  water)  with 
fat  on  a  piece  of  cloth,  how  could  you  remove  first  one  and  then 
the  other  component  of  the  mixture? 

EXERCISE   19 

SOLUBILITY  AND  TEMPERATURE.    SATURATION 

Object:  To  learn  how  to  make  a  saturated  solution,  and  to  know 
approximate  amount  dissolved  (approx.  solubility).  Also  to  study 
the  influence  of  temperature  on  solubility. 

Apparatus:  Test-tubes.  Funnel.  Watch-glass.  100  c.c.  beaker. 
Trip  scales.  Graduated  cylinder.  Thermometer. 

Materials:  Calcium  sulphate  (powdered).  Calcium  carbonate. 
Filter-paper.  Potassium  dichromate  (cryst.)  Sodium  sulphate 
(Glauber's  salt  Na2SO4,10H2O  and  anhydrous  Na^SCX).  Potas- 
sium carbonate  (cryst.).  Ammonium  chloride  (cryst.). 

a.  Test  of  Degree  of  Solubility.  Place  1  c.c.  of  powdered  cal- 
cium sulphate  in  a  test-tube  and  shake  with  10  c.c.  of  water  for 


SOLUBILITY  AND  TEMPERATURE  27 

two  or  three  minutes.  Filter  the  mixture,  catching  the  clear 
filtrate  in  a  clean  test-tube.  Treat  as  in  Ex.  11,  a,  to  see  whether 
any  dissolved  (?).  Examine  1  c.c.  of  powdered  calcium  carbon- 
ate (chalk)  in  the  same  way  (?).  Compare  the  deposits  on  the 
watch-glasses  (?).  Which  substance  is  more  soluble?  What 
conclusion  should  you  have  drawn  from  mere  shaking  with 
water,  without  completing  the  test? 

Was  the  solution  you  evaporated  saturated?  Was  it  con- 
centrated? What  is  a  saturated  solution? 

b.  Pulverize  6  g.   of  potassium  dichromate.     Describe  the 
change  in  color  and  explain  it  (?).     Shake  the  powder  with 
10  c.c.  of  water  in  a  test-tube  until  the  liquid  is  saturated.    What 
evidence  is  there  that  a  good  deal  dissolves? 

Now  warm  the  contents  of  the  test-tube  gently,  with  occa- 
sional shaking  (?).  Is  the  substance  more  or  less  soluble  as 
the  temperature  rises?  When  all  has  dissolved,  set  the  tube 
in  the  rack  and  examine  it  when  it  has  cooled  (?).  Describe 
the  contents. 

Warm  the  contents  of  the  tube  carefully  (to  avoid  cracking 
the  tube)  once  more  until  all  has  dissolved.  Then  hold  the 
tube  in  running  water  to  cool  it  rapidly  (?).  Describe  the 
contents  (?).  Note  two  differences  (in  size  of  particles  and  in 
color)  between  the  results  of  slow  and  of  rapid  cooling  and  ex- 
plain each  (?). 

c.  Supersaturated  Solution.     Heat  some  anhydrous  sodium 
sulphate  strongly  in  a  porcelain  dish  and  allow  it  to  cool.     Take 
about  10  c.c.  of  water  in  each  of  two  test-tubes.     To  one  portion 
add  Glauber's  salt,  previously  pulverized  in  a  mortar,  until, 
after  shaking,  a  considerable  excess  remains  undissolved.    Satu- 
rate the  other  portion  with  the  cold  anhydrous  sodium  sul- 
phate in  the  same  manner.     Perform  the  last  operation  rapidly, 
taking  care  not  to  introduce  any  particles  of   the   hydrate, 
and  do  not  let  the  solution  stand  before  use.     Now  decant  the 
two  liquids  into  clean  test-tubes,  disregarding  the  cloudiness 
of  one  of  them.    Then  add  a  little  of  the  anhydrous  substance 
to  the  solution  first  made  and  a  small  crystal  of  Glauber's  salt 
to  the  contents  of  the  second  test-tube  and  shake  both  (?). 
After  a  short  time,  examine  the  contents  of  each  again  (?). 
Interpret  the  results  [120]. 

d.  Properties  of  Solutions:  Volume  Changes  and  Thermal      -  JL 
Effects.    [Quant.]    Take  about  25  g.  of  potassium  carbonate 


28  HYDROGEN  CHLORIDE 

and  determine  its  weight  to  the  nearest  tenth  of  a  gram.  As- 
suming the  specific  gravity  of  this  substance  to  be  2,  calculate 
the  volume  of  the  amount  you  have  taken  (?).  Place  in  the 
graduated  cylinder  exactly  85  c.c.  of  water  and  take  its  tem- 
perature. What  is  the  sum  of  the  volumes  of  the  water  and  the 
carbonate,  separately?  Add  the  weighed  specimen  of  potas- 
sium carbonate  to  the  water,  dissolve  by  repeated  inversion  of 
the  cylinder,  closing  the  mouth  of  the  latter  with  the  hand,  and 
read  the  volume  of  the  solution  (?).  Read  also  the  temperature 
of  the  solution  immediately  (?).  Is  there  a  change  in  volume, 
or  in  temperature,  on  dissolving  these  twg  substances  in  one 
another? 

What  relation  exists  between  the  sign  of  the  thermal  effect 
when  a  substance  is  dissolved  in  a  nearly  saturated  solution  of 
the  same  substance,  and  the  change  of  solubility  with  temper- 
ature [243-5]  ?  What  do  you  infer  in  this  case? 

e.  Repeat  d,  using  about  25  g.  of  ammonium  chloride  (sp. 

.  1.5).  Make  the  same  observations  and  answer  the  same 
questions. 

EXERCISE  20 
HYDROGEN  CHLORIDE  —  PREPARATION  AND  PROPERTIES 

Object:  To  obtain  hydrogen  chloride  and  to  learn  some  of  its  proper- 
ties. 

Apparatus:  Test-tubes.  Glass  rod.  Watch-glass.  Lens  (one  for 
class). 

Materials:  Ammonium  chloride.  Calcium  chloride.  Potassium 
chloride.  Sulphuric  acid  (cone.).  Litmus  paper.  Ammonium 
hydroxide  (sol.).  Sodium  chloride.  Silver  nitrate  (sol.).  Zinc 
(dust).  Sodium-hydrogen  sulphate  (sat.  sol.). 

a.  Place  1  c.c.  of  any  chloride  (for  example  ammonium 
chloride  NH4C1,  calciuin  chloride  CaCl2,  or  potassium  chloride 
KC1)  in  a  test-tube  and  add  1  c.c.  of  concentrated  sulphuric 
acid  (?).  Is  the  material  boiling  (feel  the  bottom  of  the  tube. 
Sulphuric  acid  boils  above  300°)?  Waft  a  little  of  the  gas 
towards  the  nose,  but  do  not  bring  the  latter  too  near  to  the 
tube  (odor  ?). 

To  learn  the  behavior  of  the  gas  with  water  vapor,  blow  the 
breath  across  the  mouth  of  the  tube  (?). 


HYDROGEN  CHLORIDE  29 

Moisten  pieces  of  blue  and  of  red  litmus  paper  with  water    ' 
(to  dissolve  the  gas)  and  place  them  in  the  mouth  of  the  test- 
tube  (?).    What  chemical  property  does  the  result  show  the 
aqueous  solution  of  the  gas  to  possess? 

Dip  a  glass  rod  in  ammonium  hydroxide  solution.  Smell 
the  rod  (?).  The  gas  which  is  dissolved  in,  and  given  off  by 
this  solution  is  ammonia  (NH3).  Now  insert  the  glass  rod  into 
the  mouth  of  the  test-tube  (?).  The  product  is  formed  from 
the  ammonia  gas  and  the  hydrogen  chloride  gas. 

Light  a  wooden  splint  and  plunge  the  flame  into  the  test- 
tube  (?).  Does  the  gas  burn  or  support  combustion? 

Four  properties  of  hydrogen  chloride  (or  its  solution)  have 
been  observed.  Make  a  list  of  these,  and  note  opposite  each 
whether  it  is  a  physical  or  a  chemical  property. 

b.  Of  what  elements  is  hydrogen  chloride  composed?    What 
is  its  formula?    What  proportions  by  weight  of  the  constituents 
are  indicated  by  this  formula? 

Write  the  equation  for  the  original  action  by  which,  in  a, 
you  obtained  the  gas.  Note  that  the  three  chlorides  suggested 
will  give,  respectively,  (NH4)HS04,  CaS04,  and  KHS04,  as  one 
of  the  products.  Where  is  this  one  of  the  products?  To  which 
of  the  varieties  of  chemical  change  does  this  action  belong 
[126]? 

c.  Write  the  equation  for  the  interaction  of  ammonia  and 
hydrogen  chloride.     To  which  of  the  four  varieties  of  chemical 
change  [132]  does  this  action  appear  to  belong? 

d.  Take  1  c.c.  of  sodium  chloride  in  a  dry  test-tube  and  add 
1  c.c.  of  concentrated  sulphuric  acid  [126]. 

Place  in  a  second  test-tube  0.5  c.c.  of  silver  nitrate  solution. 
Dip  a  clean  glass  rod  in  water  and  hold  the  rod,  with  the  adhering 
water  in  the  gas  issuing  from  the  first  test-tube  for  one  minute. 
Then  transfer  the  rod,  with  the  adhering  solution,  to  the  liquid 
in  the  second  test-tube. 

To  obtain  a  better  idea  of  this  action,  add  to  the  same  silver 
nitrate  solution  one  drop  of  concentrated  hydrochloric  acid  (?). 

e.  Place  on  the  watch-glass  a  few  particles  of  zinc  dust.     Dip 
a  glass  rod  in  water,  hold  it  in  the  hydrogen  chloride  as  in  d,  and 
then  place  the  drop  of  the  aqueous  solution  of  the  gas  on  the  zinc 
dust  (?).     What  is  the  gas  liberated  (see  Ex.  9  c)?     Make  the 
equation  for  this  action  (?). 

Name  three  other  metals  which  would  react  in  a  similar  way 


30  CHLORINE 

with  hydrogen  chloride  solution  (?).  Write  equations  for  these 
three  actions  (?). 

/.  Make  the  equation  for  the  action  in  par.  1  of  d,  and  write 
the  name  of  the  substance  under  each  formula  (?). 

Take  5  c.c.  of  saturated  sodium-hydrogen  sulphate  solution. 
Add  to  it  concentrated  hydrochloric  acid,  a  very  little  at  a  time, 
shaking  the  mixture  after  each  addition  (?).  Examine  the 
precipitate  with  a  lens  and  describe  the  form  of  the  particles  (?). 
Make  the  equation  for  this  action  (?). 

Compare  the  two  equations  last  written  [127].  What  sub- 
stance, by  its  escape  as  a  gas  from  the  mixture,  permitted  the 
first  action  to  go  to  completion?  If  this  substance  had  remained 
dissolved,  what  difference  would  this  have  made  in  the  result? 
What  substance,  by  its  separation  as  a  precipitate,  permitted 
the  second  action  to  go  to  completion?  Explain  why  the 
separation  of  a  product  permits  the  completion  of  an  action  (?) 

EXERCISE  21 
CHLORINE  —  PREPARATION  AND  PROPERTIES 

Object:   To  prepare  chlorine  and  to  observe  some  of  its  properties. 
Apparatus :  Trough.     Test-tube  and  cork  to  fit.    Kipp's  hydrogen 

generator  [253]  (one  for  class).     Taper. 
Materials:   Potassium  permanganate.     Hydrochloric  acid  (cone.). 

Ammonium  hydroxide  (sol.). 
Caution:  Chlorine  gas,  when  breathed,  has  a  very  irritating 

action  in  the  throat.    Breathing  the  vapor  of  alcohol 

(sprinkled  on  a  handkerchief)  or  ammonia  gives  relief. 

Perform  the  following  experiments  in  a  HOOD,  or  place 

where  there  is  a  good  draft. 

a.  Fill  the  trough  with  water.  Place  in  the  test-tube  a  very 
few  crystals  of  potassium  permanganate  and  add  cautiously  a 
drop  or  two  of  concentrated  hydrochloric  acid  (make  sure  that 
you  do  NOT  add  some  other  acid  by  mistake).  Leave  the  tube 
open  (uncorked).  What  is  the  color  of  the  gas? 

As  soon  as  the  tube  appears  to  be  filled  with  the  gas,  close  the 
tube  quickly  with  the  cork,  invert  the  tube  instantly  in  the  water 
contained  in  the  pan  and  pull  out  the  cork.  Keeping  the  mouth 
under  the  water,  shake  the  tube  and  note  whether  or  not  the  gas 
dissolves  (?).  UL 


SODIUM  HYDROXIDE  31 

b.  Place   about   1    c.c.   of  potassium  permanganate  in  the 
300  c.c.  beaker.    Add  2-3  c.c.  of  concentrated  hydrochloric  acid 
and  cover  with  a  glass  plate. 

When  the  beaker  is  filled  with  the  gas,  move  the  plate  aside 
and  insert  for  a  few  seconds  a  jet  of  hydrogen  burning  at  a  nozzle 
attached  to  a  Kipp's  apparatus*  (?).  Keep  the  beaker  covered 
as  far  as  possible.  While  the  hydrogen  burns  in  it,  is  there  any 
change  in  the  color  of  the  gas?  Dip  a  glass  rod  in  ammonium 
hydroxide  solution  and  insert  it  into  the  gas  left  in  the  beaker 
(?).  What  gas  was  formed?  Cover  the  beaker  again  and  use 
for  c. 

c.  When  the  beaker  from  b  has  again  become  filled  with 
chlorine,  light  a  taper  and  plunge  the  flame  into  the  gas  (?). 
The  wax  of  the  taper  is  composed  chiefly  of  compounds  of  carbon 
and  hydrogen.     The  black  product  is  carbon   (soot).     What 
compound  must  have  been  formed?    Verify  your  conclusion  by 
testing  the  gas  with  ammonium  hydroxide  on  a  rod  (?). 

As  soon  as  the  last  experiment  is  finished,  take  the  beaker 
(covered)  to  the  sink,  and  pour  some  ammonium  hydroxide  solu- 
tion into  it.  •  Cover  the  beaker  again  with  the  plate  and  shake, 
holding  the  whole  over  the  sink,  and  finally  wash  out. 

d.  What  did  you  observe  that  showed  chlorine  not  to  be 
lighter  than  air?    What  two  other  physical  properties  and  two 
chemical  properties  were  observed? 


EXERCISE  22 
SODIUM  HYDROXIDE 

Object:   To  learn  some  of  the  properties  of  bases. 

Apparatus:  Test-tubes.     Glass  rod. 

Materials:  Sodium  hydroxide  (sol.).  Litmus  papers.  Cupric  sul- 
phate (sol.).  Aluminium  sulphate  (sol.).  Phenolphthalein 
(sol.).  Ammonium  hydroxide  (sol.). 

a.  Recall  the  action  of  sodium  on  water  [60],  as  seen  in  the 
class-room.  Write  the  equation  for  this  action,  and  place  the 

*  If  no  Kipp  is  available,  a  single  generating  bottle  may  be  used  for 
the  whole  class,  or  each  pupil  may  take  zinc  and  hydrochloric  acid  in 
a  bottle  provided  with  a  stopper,  L-tube,  rubber  connection,  and 
nozzle  (Fig.  10,  p.  14). 


32  PROPERTIES  OF  ACIDS 

name  of  the  substance  under  each  formula  (?).  To  which  of 
the  four  varieties  of  chemical  change  [132]  does  this  action  belong? 
6.  Take  1  c.c.  of  sodium  hydroxide  solution  and  dilute  it  with 
10  c.c.  of  water.  Dip  a  clean  glass  rod  in  the  liquid  and  taste  it. 
[Immediately  rinse  the  mouth  out  with  water.  Taste  substances 
only  when  told  to  do  so]  (?).  Dip  red  and  blue  litmus  paper  in 
the  solution  (?).  Rub  the  liquid  between  the  fingers  (?).  Use 
the  same  solution  in  c. 

c.  To  1  c.c.  of  cupric  sulphate  solution  add  one-third  of  the 
diluted  sodium  hydroxide  solution   (?).     Make  the  equation 
and  attach  to  each  formula  the  name  of  the  substance  (?).     To 
which  variety  of  chemical  change  [132]  does  this  reaction  belong? 
Where  is  the  other  product  of  the  reaction  and  how  should  you 
proceed  so  as  to  separate  the  precipitate,  and  finally  obtain  the 
other  product  in  solid  form? 

d.  To  1  c.c.  of  aluminium  sulphate  solution  add  a  few  drops 
(shake  between  drops)  of  the  sodium  hydroxide  solution  (?). 
Make  the  equation  and  answer  the  same  questions  (?). 

e.  To  the  rest  of  the  sodium  hydroxide  solution  add  one  drop 
of  phenolphthalein  solution  (?).    Litmus  and  phenolphthalein 
are  called  indicators.    How  does  each  behave  with  a  base? 

/.  What  substance  have  we  previously  found  to  have  the 
same  effect  on  phenolphthalein  as  has  sodium  hydroxide  (Ex. 
11)?  What  is  its  formula? 

Dilute  1  c.c.  of  ammonium  hydroxide  solution  with  10  c.c.  of 
water  and  try  with  it  the  tests  in  b  and  d  (?). 

g.  Make  a  list  of  the  chemical  properties  you  have  found  a 
base  to  possess  (?).  What  radical  is  common  to  all  bases,  and 
confers  these  properties? 

EXERCISE  23 
PROPERTIES  OF  ACIDS 

Object:  To  learn  about  ionization  and  ike  properties  of  adds. 
Apparatus:  Test-tubes.    Glass  rod. 

Materials:  Sodium  hydroxide.     Hydrochloric  acid  (dil.).    Litmus 
papers.     Sodium  hydroxide  (sol.).     Hydrochloric  acid  (cone.). 

a.  Place  a  small  piece  of  sodium  hydroxide  in  a  test-tube, 
add  2  c.c.  of  water,  and  shake  (?).  What  property  does  the 
solution  possess  which  the  solid  body  lacked  [175]?  Accord- 


I 


\ 


•0 

N 
> 


PROPERTIES  OF  ACIDS  33 

ing  to  the  theory  of  ionization,  what  chemical  change  took 
place  when  the  solid  dissolved?  Make  an  ionic  equation  for 
this  change  [182]. 

What  evidence,  based  on  the  freezing  and  boiling-points  of 
such  a  solution,  shows  that  this  change  has  occurred?  How 
many  new  substances  are  produced  in  this  action?  Name 
them  (?). 

6.  You  dissolved  hydrogen  chloride  in  a  drop  of  water  (Ex. 
20  d).  Answer  the  same  five  questions  as  in  a,  and  make  the 
ionic  equation. 

In  the  case  of  every  other  simple  acid,  base,  or  salt,  would  the 
answers  always  be  the  same,  or  would  they  in  some  cases  be 
different? 

c.  Take  2  c.c.  of  dilute  hydrochloric  acid  and  dilute  it  with 
10  c.c.  of  water.    Repeat  with  this  solution  the  three  tests 
described  in  Ex.  22  b,  and  record  the  results. 

d.  When  zinc  (or  one  of  certain  other  metals,  Ex.  9  d)  is 
placed  in  dilute  sulphuric  acid,  what  gas  is  liberated?  jiMake 
the  ionic  equation  for  this  action  [185]. 

All  soluble  acids  show  the  properties  found  in  c  and  d.  Make 
a  list  of  these  properties  (?). 

e.  Place  3  c.c.  of  sodium  hydroxide  solution  in  a  test-tube. 
Add  about  1  c.c.  of  concentrated  hydrochloric  acid.     Is  there 
evidence  of  chemical  action  (touch  the  back  of  the  hand  with  the 
bottom  of  the  test-tube)?    Keep  the  mixture  for  /. 

Make  the  ordinary  [173]  and  ionic  [193]  equations  for  this 
action,  which  is  a  "  neutralization." 

/.  Since  acids  and  bases  act  oppositely  on  indicators,  like 
litmus  and  phenolphthalein,  it  is  possible  to  find  out  when  the 
proportions  of  the  two  materials  required  for  complete  inter- 
action have  been  taken,  for  the  mixture  will  then  be  without 
action  on  an  indicator. 

Dilute  the  mixture  prepared  in  e.  Moisten  a  glass  rod  in 
it,  and  touch  the  edge  of  a  piece  of  blue  and  of  a  piece  of  red 
litmus  paper  with  it  (?).  If  the  blue  turns  red,  there  is  excess  of 
acid.  Add  sodium  hydroxide  solution  a  drop  at  a  time,  shaking 
between  drops,  and  moistening  the  rod  and  testing  as  before. 
Continue  until  no  effect  is  produced  on  litmus  of  either  color. 
If,  by  accident,  too  much  alkali  is  added,  or  if  the  mixture  was 
alkaline  in  the  beginning,  use  drops  of  dilute  hydrochloric  acid 
in  the  same  way. 


34 


IONIZATION 


When  the  liquid  is  neutral  to  indicators,  taste  it  by  touching 
the  tongue  with  the  glass  rod  (?). 

Set  the  solution  aside  to  evaporate  by  itself.  When  it  has 
dried  up,  examine  the  solid.  What  is  the  form  of  the  crystals? 
What  is  the  substance? 


EXERCISE  24 
IONIZATION  OF  ACIDS,  BASES,  AND  SALTS 

Object:  To  compare  the  extents  of  ionization  of  various  acids,  bases 
and  salts. 

Apparatus:  Electrolytic  cell  and  electrodes.  Storage  batteries  or 
lamp-board  (Instructor). 

Materials:  Sodium  chloride  (crystals  and  0.1  N  solution).  Sodium 
hydroxide  (0.1  N  sol.).  Hydrochloric  acid  (0.1  N  sol.).  Am- 
monium hydroxide  (0.1  N  sol.).  Acetic  acid  (0.1  N  sol.).  Am- 
monium chloride  (0.1  Nsol.).  Ammonium  acetate  (0.1  N  sol.). 
Sugar  (0.1  N  sol.).  Toluene.  Dry  hydrogen  chloride. 

a.  Ionization.  Name  several  distinct  methods  by  which 
we  may  ascertain  experimentally  whether  a  substance  is  ionized 
in  solution  or  not,  and  may  learn  the  extent  of 
the  ionization  [183-90]  (?).  Define  the  term 
ionization,  first  in  theoretical  terms  (?),  and 
second  in  terms  of  the  experimental  evidence  (?). 
The  degrees  to  which  aqueous  solutions  of 
many  substances  are  ionized  are  given  in  Ap- 
pendix II.  Constant  reference  to  this  will  be 
necessary  in  interpreting  the  observations  in 
this  and  succeeding  exercises. 

The  experiments  of  this  exercise  may  be 
postponed  until  after  the  work  in  25  or  26  has 
been  done.  The  apparatus  should  be  set  up  by 

FIG   13  *ke  instructor  and  explained  to  the  class  before 

use. 

Obtain  [Storeroom]  an  electrolytic  cell*  (Fig.  13).    Half  fill 

*  The  cell  consists  of  a  glass,  flat-bottomed,  specimen  tube  (about 
75  X  22  mm.)  fitted  with  a  two-hole  rubber  stopper  in  which  a 
vertical  groove  has  been  cut  to  permit  the  escape  of  gases.  The 
electrodes  are  pieces  of  tin  about  10  cm.  long. 


IONIZATION 


35 


no  v-b.c. 


the  cell  with  the  substances  named  below  in  turn.  See  very 
particularly  that  the  electrodes  in  the  cell  are  not  touching  one 
another.  Connect  with  the  terminals  on 
the  lamp  board*  (Fig.  15),  and  note 
whether  the  lamp  glows  or  not  (?).  The 
cell  is  in  series  with  the  lamp  and,  if  the 
lamp  glows,  the  solution  is  a  conductor.  If 
it  does  not  glow,  the  solution  is  a  non- 
conductor. Wash  the  cell  and  electrodes 
and  wipe  the  latter  very  carefully  after  each 
trial. 

The  following  substances,  or  solutions,  show 
the  behavior  typical  of  various  classes  of 
materials.  After  giving  the  result  in  your 
notes,  name  the  class  which  is  illustrated  in 
each  case. 

If  the  substance  is  a  conductor,  what  con- 
clusion is  to  be  drawn  in  regard  to  the  condi- 
tion of  the  dissolved  body?  In  each  such 
case,  write  an  equation  showing  the  materials 
present  in  the  solution,  and  write  the  name  under  the  formula 
of  each  substance  (?). 


FIG.  14a 


*  A  storage  battery  of  three  lead  cells  or  five  Edison  cells  in  series 
may  be  used,  but  is  always  in  danger  of  being  ruined  by  short-cir- 
cuiting through  carelessness.  Protection  by  means  of  a  fuse  leads 
to  continual  interruptions  of  the  work.  Where  direct  current  is 
employed  in  the  lighting  system,  the  best  plan  is  to  use  the  circuit 
through  two  resistances  of  such  ratio  to  each  other  as  to  give  the 
desired  potential  by  the  drop  over  one  of  them.  Thus,  if  we  place 
a  20-ohm,  and  a  3.5-ohm  resistance  on  a  110- volt  circuit  (Fig.  14, 
diagrammatic),  the  potential  drop  over  the  lower  resistance  will  be 
about  16.5  volts.  If  these  resistances  be  of  sufficient  carrying 
capacity  (say,  5  amperes),  then  four  different  current  outlets  may  be 
provided  —  each  one  with  plenty  of  current  for  one  of  the  elec- 
trolytic cells  previously  described.  Each  of  these  outlets  is  in  series 
with  a  small  battery  lamp,  used  as  an  indicator  of  the  flow  of  current 
through  the  cell  (Fig.  15). 

Where  alternating  current  only  is  available,  a  small  rotary  trans- 
former, now  commonly  employed  for  charging  automobile  batteries, 
may  be  used. 


36  IONIC  MATERIALS 

1.  Dry,  crystallized  sodium  chloride  (?). 

2.  Distilled  water  (?). 

3.  0.1  N  aqueous  solution  of  sodium  chloride  (?). 

4.  0.1  N  aqueous  solution  of  sodium  hydroxide  (?). 

5.  0.1  N  aqueous  solution  of  hydrogen  chloride  (?). 

6.  0.1  N  aqueous  solution  of  ammonium  hydroxide  (?), 

7.  0.1  N  aqueous  solution  of  acetic  acid  (?). 

8.  0.1  N  aqueous  solution  of  ammonium  chloride  (?). 

9.  0.1  N  aqueous  solution  of  ammonium  acetate  (?). 

10.  0.1  N  aqueous  solution  of  sugar  (?).     Now,  dry  the  cell  by 
washing  first  with  alcohol  and  then  with  ether. 

11.  Toluene  in  the  dried  cell  (?). 

12.  Hydrogen  chloride  dissolved  in  dry  toluene  (?).    What 


Ho  0A/T7.S  Resistance 

60  Watt.   Ward-  Leonard 
$£  Ohms  Resistance 


FIG.  15 

difference  between  water  and  toluene  do  tests  5  and  12  bring  to 
light?  Keep  this  solution  corked  up  in  a  dry  test-tube  for  use 
in  28  d. 

EXERCISE  25 
IONIC  MATERIALS 

a.  Ionic  Materials.  Give  the  names  and  symbols  (not  for- 
getting the  charges)  of  the  three  distinct  substances  (in  addition 
to  water)  present  in  the  aqueous  solution  of  sodium  chloride 


b.  Give  a  concise  comparative  statement  of  the  specific  physi- 
cal properties  (such  as  color,  molecular  weight,  solubility,  be- 
havior towards  electrically  charged  bodies,  physical  state,  etc.), 
of  the  ionic  and  the  free  forms  of  sodium,  hydrogen,  and  chlo- 
rine (?).  . 


UNDISSOCIATED  SUBSTANCE  AND  ITS  IONS       37 


EXERCISE  26 

EQUILIBRIUM    BETWEEN   UNDISSOCIATED   SUBSTANCE  AND  ITS 

IONS 

Object:  To  study  the  equilibrium  between  the  ionized  and  non-ionized 
parts  of  an  electrolyte  in  solution. 

Apparatus :  Test  tubes.    Glass  rod. 

Materials:  Potassium  bromide  (crystals).  Cupric  bromide  (crys- 
tals). Cupric  chloride  (crystals).  Cobalt  chloride  (sol.). 
Potassium  permanganate  (sol.).  Potassium  dichromate  (sol.). 
Chrome-alum  (crystals). 

Relations  of  the  Undissociated  Substance  to  its  Constituent 
Ionic  Substances  (in  Equilibrium).  The  ions  of  an  electro- 
lyte and  the  remaining  molecules  are  in  chemical  equilibrium 
[182].  What  changes  take  place,  respectively,  when  the  solution 
is  concentrated  by  evaporation  and  when  it  is  diluted,  as  in  a, 
below  [188]?  Can  the  proportion  of  molecules  be  increased 
otherwise  than  by  concentrating  the  solution  (see  6,  below) 
[455]?  With  substances  like  sodium  chloride  and  hydrogen 
chloride  these  changes  cannot  be  perceived  by  the  eye  (why?). 
In  the  following  instances  (a  and  b)  the  ionic  and  undissociated 
substances  are  both  perceptible  to  the  eye,  and  their  relations  as 
described  above  may,  therefore,  be  studied  very  easily. 

a.  Make  a  solution  of  potassium  bromide  in  water.    What  is 
the  color  of  bromide-ion?    Take  0.5  g.  of  cupric  bromide  in  a 
dry  test-tube.    Add  two  drops  of  water  and  agitate  for  some  time 
(?).    Then  add  more  water,  a  drop  or  two  at  a  time,  agitating 
vigorously,  and  giving  the  substance  time  to  dissolve,  if  it  can, 
after  each  addition.     Continue  the  addition  of  water  cautiously 
until  the  substance  has  all  dissolved,  and  afterward  until  the 
change  in  color  is  complete,  and  then  stop.    What  is  the  color 
of  the  molecules  of  cupric  bromide?    What  is  the  .color  of  cupric- 
ion?    Compare  the  color  with  that  of  cupric  sulphate  solution 
(?)  and  explain.     Formulate  the  change  which  has  been  wit- 
nessed (?). 

b.  Now  take  a  fresh  portion  of  cupric  bromide  and  repeat 
the  experiment  as  in  a,  stopping  the  addition  of  water  at  the 
green  stage.    Divide  the  mixture  into  two  parts.    To  one  add 


38      DECOMPOSITIONS  BETWEEN  ELECTROLYTES 

2-3  g.  of  solid  potassium  bromide  and  shake  vigorously  (?). 
To  the  other  portion  add  4-5  g.  of  solid  cupric  chloride  (?). 
Interpret  the  results. 

The  converse  case,  in  which  one  of  the  ions  is  removed,  and 
the  dissociation  is  promoted,  is  discussed  in  d. 

c.  Many  ionic  substances  are  colored,  although  the  color  does 
not  always  differ  markedly  from  that  of  the  molecules.     Examine 
the  following  solutions,  make  a  list  of  the  ionic  substances  con- 
tained in  them,  with  their  formulae  and  charges,  and  note  the 
color  of  each  kind  of  ions:   cobalt  chloride,  potassium  perman- 
ganate, potassium  dichromate,  chrome-alum  (this  last  solution 
freshly  made  by  dissolving  the  solid). 

d.  Just  as  the  union  of  ions  to  form  molecules  may  be  pro- 
moted by  addition  of  a  substance  yielding  a  common  ion  (? 
Ex.  26  6),  so  the  reverse  of  this,  namely,  the  dissociation  of  mole- 
cules into  ions,  may  be  promoted  by  the  removal  of  one  of  the 
ionic  materials.    The  removal  of  ions  may  be  accomplished  in 
several  ways. 

(1)  By  union  of  the  ion  with  some  other  ion,  when  the  mole- 
cules thus  formed  are  insoluble.    This  case  will  be  illustrated 
next  (see  Ex.  27). 

(2)  By  union  of  the  ion  with  some  other  ion,  when  the  mole- 
cules thus  formed,  although  soluble,  are  very  little  dissociated 
by  water  (see  Ex.  29). 

(3)  By  discharge  of  the  ion  and  liberation  of  its  material, 
through  transfer  of  the  charge  to  another  substance  (see  Ex.  31). 

(4)  By  decomposition  of  the  ion,  as  in  Ex.  6  e. 

(5)  By  the  mere  change  in  the  valence  (amount  of  the  charge) 
of  an  ion,  for  this  converts  it  into  another  substance  of  the  same 
material  composition. 

(6)  By  discharge  of  the  ion  and  liberation  of  its  material 
through  electrolysis.    This  was  illustrated  in  Ex.  24. 


EXERCISE  27 

DOUBLE  DECOMPOSITIONS  BETWEEN  ELECTROLYTES 
IN  SOLUTION 

Object:   To  study  some  typical  double  decompositions  between  electro- 
lytes in  solution. 
Apparatus:  Test-tubes.    Funnel.    Watch-glass.    Bunsen. 


DECOMPOSITIONS  BETWEEN  ELECTROLYTES      39 

Materials:  Silver  nitrate  (sol.).  Potassium  chloride  (sol.).  Cal- 
cium chloride  (sol.).  Sodium  hydroxide  (sol.).  Cupric  sul- 
phate (sol.).  Hydrochloric  acid  (dil.). 

a.  Precipitation.  Place  3-4  c.c.  of  silver  nitrate  solution  in 
a  test-tube  and  dilute  with  water.  Add  potassium  chloride 
solution  cautiously  and  agitate  continuously,  until  no  further 
precipitation  occurs  (?).  Filter,  concentrate  the  nitrate  by 
evaporation,  and  pour  it  into  a  watch-glass  to  crystallize  (?). 
Two  salts  are  obtained,  one  by  precipitation  and  one  by  evapo- 
rating. 
Formulate  the  action  (as  shown  below).  In  doing  this,  show  the 

KC1  +±  K+     +  01- 
AgN03  *±  N03-  +  Ag+ 

I  Ti 

KN03       AgCl  (dissolved.) 

Ti 
AgCl  (solid) 

three  main  physical  components  of  each  of  the  original  solutions 
and  the  relations  of  these  components  (in  equilibrium)  to  one 
another  in  each  case.  Show  also  the  molecular  products  formed 
when  the  solutions  are  mixed.  Assuming  that  the  solutions  are 
approximately  decinormal  [189],  ascertain  the  proportions  in 
which  the  original  components  of  the  solutions  are  present  before 
mixing  (Appendix  II).  Learn  also  to  what  extent  the  molecular 
products  will  be  formed  by  union  of  the  ions  [189]  (Appendix  II) 
and,  in  the  case  of  an  insoluble  substance,  how  complete  will  be 
the  precipitation  (Intermediate  Chemistry,  table  on  inside  of 
front  cover).  On  the  basis  of  this  complete  information,  com- 
plete the  formulation,  using  heavy  arrows  to  show  the  main  ten- 
dency in  each  equilibrium.  Explain  in  detail,  and  one  by  one,  in 
what  way,  and  to  what  extent,  each  of  the  six  original  components 
is  affected  by  the  results  of  mixing. 

Name  the  components  of  the  filtrate  and  explain  how  each  is 
affected  by  the  evaporation  and  crystallization. 

How  does  the  formation  of  the  precipitate  of  silver  chloride 
illustrate  Ex.  26  d  (1)?  Upon  what  factor  does  the  complete- 
ness of  the  change  depend?  Is,  or  is  not,  silver  chloride  a  highly 
ionized  substance  [176]? 

Aside  from  double  decompositions,  what  means  have  we  for 
learning  of  what  radicals  a  salt  (like  silver  nitrate)  is  composed? 


40  BASES  AND  ACIDS 

b.  To  a  little  calcium  chloride  solution  in  a  test-tube  add 
sodium  hydroxide  solution  (?).    Exactly  as  in  Ex.  27  a  (second 
par.),  formulate,  study  and  explain  the  whole  action.    How 
does  this  illustrate  (1)  of  Ex.  26  dl 

To  what  classes  of  electrolytes  do  the  four  molecular  substances 
respectively  belong? 

c.  To  a  little  cupric  sulphate  solution  add  a  little  dilute  hydro- 
chloric acid  (?).     In  what  respects  does  the  result  differ  from 
those  in  a  and  6,  and  why?    Can  any  acids  be  prepared  by 
precipitation,  and  if  so,  which  [364]? 

In  future,  formulate  all  ionic  actions  in  the  way  indicated  in  a. 

EXERCISE  28 
BASES  AND  ACIDS 

Object:   To  learn  the  properties  of  bases  and  adds. 
Apparatus :  Test-tubes.     File.     Porcelain  dish.     Bunsen. 
Materials:  Litmus   (sol.).     Phenolphthalein   (sol.).     Sodium  hy- 
droxide.    Hydrochloric  acid.     Marble.     Iron  nail.     Toluene. 

a.  Bases  and  Acids:  Hydroxide-ion  and  Hydrogen-ion:  In- 
dicators.   Examine  distilled  water  in  respect  to  (a)  taste,  (b) 
behavior  with  litmus,  (c)  conductivity  (done  already,  Ex.  24). 

b.  Dissolve  a  small  piece  of  sodium  hydroxide  in  water  and 
examine  the  solution  in  respect  to  (a)  taste,  by  diluting  a  little 
and  tasting  one  drop,  (b)  behavior  with  litmus,  (c)  behavior 
with  phenolphthalein,   (d)   conductivity  (see  Ex.  24).     These 
properties  belong  to  aqueous  solutions  of  all  bases.    Aside  from 
the  water,  what  component  alone  is  common  to  all  solutions  of 
bases,  and  has  the  above  properties?    Name  this  component 
and  give  its  formula  (?). 

c.  Examine  an  aqueous  solution  of  hydrochloric  acid  in  respect 
to   (a)  taste,   (b)  behavior  toward  litmus,   (c)  behavior  with 
phenolphthalein,  (d)  conductivity  (see  Ex.  24),  (e)  action  on  a 
piece  of  marble,  (f)  action  on  an  iron  nail  (clean  this  with  the 
file  before  use).     These  properties  are  shown  by  all  aqueous 
solutions  of  acids.    Aside  from  the  water,  what  component  alone 
is  common  to  all  solutions  of  acids,  and  has  these  properties? 
Name  and  give  the  formula  of  this  component  (?). 

d.  Take  the  solution  of  hydrogen  chloride  in  toluene  (Ex.  24) 


NEUTRALIZATION  41 

and  examine  it  in  respect  to  (a)  conductivity  (done  already, 
Ex.  24),  (b)  action  on  a  piece  of  marble,  dried  in  advance  by 
heating  in  a  dry  porcelain  dish  for  a  few  moments,  (c)  action  on 
an  iron  nail  (clean  as  before).  Be  sure  that  perfectly  dry  vessels 
are  used  in  these  experiments.  What  substance  identified  in 
c  is  absent  from  this  solution?  What  difference  between  water 
and  toluene,  as  solvents,  does  this  result  indicate?  In  what 
three  other  respects  would  the  two  solutions  of  hydrogen  chloride 
be  found  to  differ? 


EXERCISE  29 
NEUTRALIZATION 

Object :   To  investigate  the  action  of  a  strong  add  on  a  strong  base. 
Apparatus:  Laboratory    scales.     Graduated    cylinder.     Burettes. 

Beakers.     Glass  rod.     Sandbath.     Bunsen. 
Materials:    Potassium    hydroxide.       Hydrochloric    acid    (cone.). 

Phenolphthalein  solution. 

a.  Neutralization  (Union  of  H+  and  OH~).  A  considerable 
chemical  change  may  occur  not  only  in  precipitation  (see  Ex.  27), 
but  also  when  ions  unite  to  form  a  substance  which,  although 
soluble,  is  very  little  ionized  by  water. 

Weigh  out  5  g.  (laboratory  scales)  of  potassium  hydroxide, 
dissolve  it  in  a  little  distilled  water  in  the  graduated  cylinder, 
add  water  until  the  total  volume  is  50  c.c.,  and  pour  the  clear 
solution  into  a  burette.  Measure  10  c.c.  of  concentrated  hydro- 
chloric acid  in  the  graduated  cylinder,  mix  it  in  a  small  beaker 
with  50  c.c.  of  distilled  water,  and  pour  this  into  a  second  burette. 
Now,  into  a  small  beaker  or  flask  run  15  c.c.  of  the  acid  solution 
from  the  second  burette,  and  then  add  to  it  two  drops  of  phe- 
nolphthalein  solution.  Place  the  vessel  under  the  first  burette, 
read  the  level  of  the  liquid  in  the  burette,  and  allow  the  alkali 
to  run  into  the  acid  drop  by  drop,  stirring  constantly,  until  the 
last  drop  confers  the  faintest  perceptible  pink  tinge  on  the  whole 
solution.  If  you  do  not  at  first  succeed  in  stopping  at  .the  right 
point,  repeat  the  experiment.  Note  the  volume  of  alkali  used. 
Concentrate  the  solution  on  the  sand  bath  until  a  drop  deposits 
crystals  on  cooling,  and  then  remove  the  dish  from  the  sand  bath 
promptly  and  set  it  aside. 


42  SOLUTION  OF  AN  INSOLUBLE  BASE 

When  sufficient  crystals  have  appeared,  dry  them  with  filter 
paper  and  examine  with  respect  to  (a)  form,  (b)  taste,  (c)  ex- 
posure to  moist  air,  (d)  action  of  a  solution  on  litmus,  (e)  con- 
ductivity of  aqueous  solution  (done  already,  Ex.  24).  Construct 
a  table  comparing  the  substance  in  these  respects  with  the 
materials  from  which  it  was  made.  Compare  the  substance 
with  potassium  chloride.  How  should  you  determine  whether 
a  substance  obtained  in  this  way  contained  water  of  hydration 
or  not?  Make  the  necessary  experiments  (?).  Wash  out  the 
burettes. 

Following  the  directions  in  Ex.  27  a  (second  par.),  formulate, 
study,  and  explain  the  whole  action.  Note,  however,  that  there 
are  here  no  insoluble  substances.  Show  how  this  experiment 
illustrates  Ex.  26  d  (2). 

Express  the  change  involved  in  every  neutralization  of  highly 
ionized  substances  by  means  of  the  simplest  equation.  How 
may  neutralization  be  defined,  in  terms  of  the  hypothesis  of 
ions?  How  may  it  be  defined,  taking  account  of  all  the  facts, 
but  omitting  all  reference  to  ions? 

Calculate  the  approximate  concentration,  in  terms  of  a  normal 
solution  as  unity,  of  the  potassium  hydroxide  solution  used  above 
(?).  From  the  volumes  of  alkali  and  acid  used  in  neutralizing, 
calculate  the  concentrations  of  the  diluted  hydrochloric  acid  (?), 
and  of  the  concentrated  acid  employed  to  make  it  (?),  expressing 
the  concentrations  in  terms  of  a  normal  solution.  Calculate  the 
number  of  grams  of  hydrogen  chloride  per  liter  in  the  dilute  and 
concentrated  acids,  respectively  (?). 

6.  Neutralization  of  Slightly  Ionized  and  of  Insoluble  Sub- 
stances. Consider  the  degree  of  ionization  of  acetic  acid  (Ap- 
pendix II).  To  neutralize  1  liter  of  normal  acetic  acid,  would 
more  or  less  alkali  be  required  than  to  neutralize  1  liter  of  normal 
hydrochloric  acid?  In  what  way,  precisely,  would  the  details 
of  the  change  be  different  in  the  case  of  acetic  acid  [Appen- 
dix II]?  Name  some  of  the  consequences  of  this  difference. 

EXERCISE  30 

SOLUTION  OF  AN  INSOLUBLE  BASE  BY  A  STRONG  ACID 

Object:   To  investigate  the  action  of  a  strong  add  on  a  weak,  insoluble 
base. 


DISPLACEMENT  43 

Apparatus:  Beakers.     Funnel.     Test-tube/  ,;cWash-bottle.     Sand- 

bath. 
Materials:    Cupric    sulphate    (sol.).      S^uum    hydroxide  *(sol.). 

Hydrochloric  acid  (dil.). 

a.  Dilute  a  few  drops  of  cupric  sulphate  solution  with  much 
water  and  add  excess  of  sodium  hydroxide  solution  (?).  Fit  a 
filter  paper  properly  into  a  funnel  (Fig.  5,  p.  6).  Filter  the  mix- 
ture, and  wash  the  precipitate  (?)  and  filter  paper  repeatedly 
with  distilled  water  to  remove  soluble  substances.  Now  place 
a  clean  test-tube  below  the  funnel,  perforate  the  bottom  of  the 
filter  paper,  and  wash  the  precipitate  through  into  the  test-tube 
by  means  of  a  stream  of  water  from  the  wash-bottle.  To  the 
suspended  cupric  hydroxide,  cautiously  add  dilute  hydrochloric 
acid  in  amount  just  sufficient  to  give  a  clear  liquid.  Concen- 
trate the  liquid  on  the  sand  bath  until  a  drop,  removed  to  a 
watch-glass,  shows  signs  of  crystallizing  when  cold.  Then 
remove  the  dish  promptly  from  the  sand  bath  and  allow  it  to 
cool.  Examine  the  crystals  (?). 

Formulate  this  action  as  in  Ex.  27  a,  taking  account,  however, 
of  the  fact  that  one  of  the  interacting  substances  is  an  "  insol- 
uble" solid.  Describe  in  detail  the  stages  through  which  the 
final  production  of  solid  cupric  chloride  is  accomplished. 

To  what  class  of  ionic  chemical  changes  does  the  foregoing 
action  belong?  Answer  the  same  questions  in  regard  to  the  pre- 
cipitations of  salts  in  Ex.  27. 

EXERCISE  31 
DISPLACEMENT 


Object:   To  establish  the  order  of  a<9^ty  of  zinc  and 
Apparatus:   Beaker.     Test-tubes.     Funnel. 

Materials:   Zinc  (granulated).     Cupric  sulphate  (sol.).     Zinc  sul- 
phate (sol.).     Ammonium  sulphide  (sol.). 

a.  Displacement.  Place  several  pieces  of  granulated  zinc 
in  a  dilute  solution  of  cupric  sulphate  and  set  aside  until  the 
change  is  complete  (test  ?).  Occasional  agitation  will  hasten 
the  change  (why  ?).  Filter.  What  is  the  precipitate  [186]? 
Preserve  the  filtrate. 

Before  examining  the  filtrate,  take  a  few  drops  of  cupric  sul- 


44  NON-IONIC  ACTIONS 

phate  solution  and  a  like  amount  of  zinc  sulphate  solution  in 
two  test-tubes.  Dilute  each  solution  with  water,  and  add  to 
each  ammonium  sulphide  solution  (?).  What  is  the  precipitate 
in  each  case,  and  what  ions  are  required  to  form  it? 

To  the  filtrate  from  the  first  part  of  this  experiment  add 
ammonium  sulphide  solution  (?).  What  ions  were  present  in 
the  filtrate?  What  changes  did  the  metallic  zinc  and  the  cupric 
ions,  respectively,  undergo  in  the  first  part  of  the  experiment? 
Formulate  this  change  in  #n  equation.  In  the  course  of  this 
experiment,  what  becomes  of  the  molecular  cupric  sulphate 
(Ex.  26  d)? 

What  substances  could  have  been  substituted  for  the  cupric 
sulphate  without  affecting  the  result  so  far  as  the  consumption 
of  zinc  and  the  precipitation  of  copper  were  concerned?  What 
substances,  besides  zinc,  would  have  precipitated  copper  [54]? 
What  other  elements,  besides  copper,  are  displaced  by  zinc? 

Which  one  of  the  elements  displaced  by  zinc  did  we  prepare 
in  quantity  by  an  action  like  the  present  (Ex.  10)?  Formulate 
this  action  in  terms  of  ions.  What  were  the  products  of  the 
action  of  zinc  upon  concentrated  sulphuric  acid? 

b.  Formulate  the  following  actions  in  terms  of  the  hypothesis 
of  ions: 

Free  chlorine  and  bromide-ion. 

Free  chlorine  and  iodide-ion. 

Free  bromine  and  iodide-ion. 

Free  iodine  and  sulphide-ion. 

Arrange  these  four  elements  in  a  series  similar  to  the  electro- 
motive series  of  the  metals  [209].  Where  should  you  place 
fluorine  in  this  series? 

EXERCISE  32 
NON-IONIC  ACTIONS 

a.  Non-Ionic  Actions.  In  previous  class-room  and  labora- 
tory experiments  we  have  observed  the  formation  of  electrolytes 
in  other  ways  than  those  illustrated  in  this  chapter.  These  ways 
are  non-ionic,  or  not  distinctly  ionic.  Give  illustrations  of  such 
of  these  ways  as  you  recall:  acids,  two  ways,  bases,  one  way; 
salts,  four  ways,  together  with  the  reference  numbers  of  the 
laboratory  experiments  in  which  they  occur  (?). 


TITRATION  OF  BASES  AND  OF  ACIDS  45 

EXERCISE  33 
TITRATION  OF  BASES  AND  OF  ACIDS 

Object:   To  learn  how  to  measure  the  quantity  of  an  add  or  of  a  base 

continued  in  a  given  specimen  (quantitative). 
Apparatus :   Burette.     Beaker.     Glass  rod. 
Materials:   Normal     acid.     Sodium     hydroxide     (sol.).     Phenol- 

phthalein  (sol.).     Vinegar  (white).     Litmus  (sol.). 

a.  A  normal  solution  of  any  acid  is  one  containing  1.008  g.  of 
the  hydrogen  radical  (H)  per  liter,  accompanied,  of  course,  by  an 
equivalent  amount  of  the  negative  radical  of  that  acid.     Thus, 
one  liter  of  normal  hydrochloric  acid  (HC1)  will  contain  1.008  + 
35.46  g.  of  the  acid.     Similarly,  a  normal  solution  of  a  base 
contains  17.008  g.  of  hydroxyl  radical  (OH)  per  liter.     Thus  one 
liter  of  normal  sodium  hydroxide  (NaOH)  will  contain  23.00  + 
17.008  g.  of  the  base.     What  weight  of  acetic  acid  (H)(C02CH3) 
is  contained  in  one  liter  of  the  normal  acid?    What  weight  of 
potassium  hydroxide  in  one  liter  of  the  normal  solution  of  this 
base? 

b.  Titration  of  a  Base  with  a  Standard  Acid.    Fill  a  burette 
with  the  normal  acid.    Allow  some  of  the  acid  to  flow  out,  until 
all  air  has  been  expelled  from  the  tip,  and  until  the  meniscus  has 
reached  the  graduated  portion  of  the  burette.    Hold  the  burette 
so  that  the  surface  of  the  acid  is  on  the  same  level  with  the  eye, 
and  read  the  level  of  the  bottom  of  the  meniscus.     Observe  that 
the  graduation  is  downwards,  so  that  a  reading  two-tenths  of 
a  c.c.  above  the  2  c.c.  mark  is  1.8  c.c.  (not  2.2.  c.c.).     Record  the 
reading  (?). 

Take  exactly  10  c.c.  of  sodium  hydroxide  solution  in  the 
graduated  cylinder  (dry  this  first).  Pour  it  into  a  beaker. 
Rinse  out  the  cylinder  three  times  with  a  little  water  (about 
5  c.c.  each  time).  Set  the  beaker  on  a  sheet  of  white  paper  under 
the  burette,  and  add  a  drop  or  two  of  phenolphthalein  solution 
(?).  Stir  vigorously  with  a  very  thin  glass  rod. 

Now  allow  the  acid  to  run  in  a  rapid  succession  of  drops  into 
the  beaker.  Stir  vigorously  after  each  addition  of  a  few  drops. 
As  soon  as  the  acid  begins  to  decolorize  the  indicator  round  the 
point  where  it  enters,  proceed  more  cautiously.  Add  only  one 
drop  at  a  time,  and  stir.  The  aim  is  to  have  the  solution  dis- 


46  TITRATION  OF  BASES  AND  OF  ACIDS 

tinctly  pink  before  the  final  drop  of  acid  is  added,  and  perfectly 
colorless  when  that  drop  has  been  allowed  to  flow  in.     If,  at  the 
first  attempt,  you  overshoot  the  mark,  wash  out  the  beaker, 
and  take  a  fresh  portion  of  sodium  hydroxide  solution,  read  the  ' ' 
level  of  the  acid  in  the  burette,  and  try  again. 

When  the  titration  has  been  successfully  performed,  read 
the  level  of  the  acid  in  the  burette  (?).  Subtract  the  reading 
from  that  at  the  beginning  (?).  The  difference  (?)  is  the  volume 
of  normal  acid  required  for  complete  interaction  with  (neutraliza- 
tion of)  10  c.c.  of  the  solution  of  the  base. 

c.  Since  one  liter  of  the  normal  acid  contains  1.008  g.  of  avail- 
able hydrogen,  1  c.c.  of  the  acid  contains  0.001008  g.  of  hydrogen 
radical.     Calculate  the  weight  of  hydrogen  radical  used  in  your 
experiment  (?) .     How  many  figures  in  your  result  are  significant? 
Neglect  all  figures,  in  subsequent  calculations,  beyond  your 
limit  of  experimental  error. 

Now,  1.008  g.  of  hydrogen  radical  interacts  with  17.008  g.  of 
hydroxyl  (OH).  Using  the  weight  of  hydrogen  just  found,  cal- 
culate the  weight  of  hydroxyl  contained  in  the  portion  of  base 
you  took  (?). 

Finally,  using  the  proportion  indicated  in  the  formula  NaOH, 
calculate  the  total  weight  of  sodium  hydroxide  which  contains 
the  weight  of  hydroxyl  you  found  (?). 

d.  Knowing  from  the  result  of  c  the  weight  of  sodium  hy- 
droxide in  10  c.c.  of  the  solution,  calculate  the  weight  per  liter  (?). 

Calculate  the  concentration  of  the  solution  in  terms  of  a  nor- 
mal solution  of  sodium  hydroxide  as  unity  (?). 

e.  Titration  of  an  Acid.    Wash  out  the  burette,  fill  it  with 
the  sodium  hydroxide  solution  as  in  6,  and  read  the  level  of  the 
meniscus  (?). 

In  c,  par.  2,  we  found  the  weight  of  hydroxyl  in  10  c.c.  of  this 
solution.  Calculate  the  weight  in  1  c.c.  (?).  We  may  now  use 
this  solution  containing  a  known  concentration  of  a  base  for 
measuring  quantities  of  acids. 

/.  Take  exactly  10  c.c.  of  white  vinegar  in  the  graduated 
cylinder  (dry  this  first).  Pour  it  into  a  beaker,  rinse  the  cyl- 
inder three  times  with  water,  and  set  the  beaker  on  a  piece  of 
white  paper  under  the  burette.  Add  4  drops  of  litmus  solution, 
or  enough  to  give  the  liquid  a  distinct,  but  not  strong  pink  color. 
Stir  with  a  thin  glass  rod. 

Now  titrate  this  solution  with  that  in  the  burette,  exactly 


BROMINE  47 

as  described  in  b  (third  par.).  In  this  instance  the  color  ap- 
pears locally  with  the  blue.  Aim  to  stop  when  the  tint  is 
pinkish-violet,  halfway  between  pink  and  blue.  Repeat,  if 
necessary  to  secure  a  sharp  result.  Then  read  the  level  of  the 
meniscus  (?)  and  subtract  from  the  former  reading  to  learn  the' 
volume  of  base  used  (?). 

g.  Using  the  weight  of  hydroxyl  per  c.c.  found  in  e  (second 
par.),  calculate  the  weight  of  hydroxyl  used  in/  (?). 

Calculate  the  weight  of  acid  hydrogen  in  the  10  c.c.  of 
vinegar  (?). 

Finally,  using  the  formula  of  acetic  acid  (H)(C02CH3), 
calculate  the  total  weight  of  acetic  acid  in  the  10  c.c.  of  vinegar 
(?)..  How  much  is  this  per  liter?  What  per  cent? 

These  methods,  and  others  like  them,  are  known  as  volu- 
metric methods,  and  are  largely  used  in  analyses  made  for 
commercial  (as  well  as  scientific)  purposes. 


EXERCISE  34 
BROMINE 

Object:  To  liberate  bromine,  to  note  its  properties,  and  to  try  a  test 
for  bromides. 

Apparatus:  Test-tubes.    Mortar. 

Materials:  Potassium  bromide.  Sulphuric  acid  (cone.).  Man- 
ganese dioxide  (powdered).  Bromine.  Carbon  disulphide. 
Bromine-water.  Chlorine-water. 

a.  Take  1  c.c.  of  water  in  a  test-tube  and  add  slowly  2  c.c. 
of  concentrated  sulphuric  acid.     Pulverize  about  0.5  c.c.  of 
potassium  bromide,  add  1  c.c.  of  manganese  dioxide,  mix,  and         ir 
add  the  mixture  to  the  diluted  acid.     Warm  very  gently  with   Jr*'* 
a  small  flame  (?).     Note  the  color  (?)  and  odor  [CAUTION]  (?)  J 

of  the  vapor.    What  was  the  color  of  the  potassium  bromide?   ^~ 
Does  a  compound  show  the  colors  of  elements  contained  in  it? 
Should  you  expect  it  to  do  so? 

If  any  of  the  bromine  vapor  is  condensing  on  the  sides  of  the 
tube,  describe  its  properties  (?).  Fill  the  tube  up  with  water. 
Write  the  equation  [200]  (?). 

b.  To  about  10  c.c.  of  water  in  a  test-tube  add  two  drops  of 
bromine  [CAUTION:  Do  not  spill  upon  the  hands  (200)].    Is  the 


48  IODINE 

bromine  heavier  or  lighter  than  water?    Shake.    Is  it  soluble 
in  water?    Use  this  bromine-water  in  c. 

c.  To  10  c.c.  of  water  add  about  2  c.c.  of  carbon  disulphide, 
close  with  the  thumb,  and  shake  (?).    Are  the  liquids  miscible 
(mutually  soluble)? 

To  this  mixture  add  a  few  drops  of  bromine-water  from  6  and 
shake.  Is  the  bromine,  judging  by  the  color,  equally  soluble  in 
both  water  and  disulphide?  If  more  so  in  one,  how  much  more 
(?)  and  in  which? 

d.  Test  for  a  Bromide.    Take  a  crystal  of  potassium  bromide 
(color?)  and  dissolve  it  in  5  c.c.  of  water  (color  of  solution  ?J. 
Add  2  c.c.  of  carbon  disulphide  and  shake  (?).    Why  is  the  car- 
bon disulphide  not  colored  by  the  bromine? 

Holding  the  tube  steady,  add  now  a  drop  or  two  of  chlorine- 
water,  and  observe  carefully  whether  any  color  appears,  and, 
if  so,  in  which  layer  of  liquid  (water  layer  or  carbon  disulphide) 
it  makes  its  appearance  (?).  Why?  Shake  vigorously  and 
allow  the  mixture  to  settle  (?).  What  substance  has  been 
liberated?  Write  the  equation  [202]  (?). 

e.  Summarize  the  properties  of  bromine:   color  (?),  odor  (?), 
density  of  vapor  compared  with  air  (?),  density  of  liquid  com- 
pared with  water  (?),  relative  solubility  in  water  and  carbon 
disulphide  (?). 

Has  bromine  or  chlorine  the  greater  affinity  for  potassium? 

EXERCISE  35 
IODINE 

Object:  To  prepare  some  iodine  and  use  it  to  observe  the  properties 
of  iodine.  Also  to  try  a  test  for  iodides. 

Apparatus:  Evaporating  dish.  Mortar.  400  c.c.  beaker.  Test- 
tubes. 

Materials:  Sulphuric  acid.  Potassium  iodide.  Manganese  di- 
oxide (powdered).  Alcohol.  Carbon  disulphide.  Potassium 
iodide  (sol.).  Splints.  Chlorine-water.  Bromine-water. 

a.  Pour  into  the  evaporating  dish  1  c.c.  of  water  and  add 
2  c.c.  of  concentrated  sulphuric  acid.  Pulverize  finely  about 
1  c.c.  of  potassium  iodide,  add  2  c.c.  of  manganese  dioxide, 
mix,  and  add  the  mixture  to  the  acid.  Place  the  evaporating 
dish  upon  the  ring  on  the  stand  and  set  the  beaker  with  about 


IODINE  49 

50  c.c.  of  water  upon  it  so  that  the  vapor  of  the  iodine  may 
condense  on  the  bottom  of  the  beaker. 

Heat  the  mixture  gently  with  a  very  small  flame,  which  does 
not  touch  the  dish.  Observe  the  color  of  the  vapor  (?),  and 
the  crystals  (form  ?)  on  the  bottom  of  the  beaker.  What  was 
the  color  of  the  potassium  iodide  (?),  and  the  form  of  its  crystals? 
Are  its  crystals  like  those  of  iodine  either  in  form  or  color?  While 
the  crystals  are  accumulating,  proceed  with  d. 

b.  Place  in  as  many  test-tubes  1  c.c.  each  of  water,  alcohol, 
carbon  disulphide,  and  potassium  iodide  solution.     Scrape  some 
of  the  crystals  of  iodine  off  the  bottom  of  the  beaker  with  a 
wooden  splint,  add  one  crystal  to  the  contents  of  each  of  the  four 
test-tubes  and  shake  (?).    Is  the  iodine  heavier  or  lighter  than 
water? 

Tabulate  the  results  as  follows,  giving  the  solvent  (?),  degree 
of  solubility  (slight,  considerable,  very  great  ?),  and  the  color  of 
the  solution  (look  through  it  at  a  piece  of  white  paper  ?) : 

SOLVENT  SOLUBILITY  COLOR  OF  SOLUTION 

Water: 
Etc.: 

*  The  solution  in  alcohol  is  the  lotion  called  "tincture  of  iodine." 
That  in  potassium  iodide  solution  is  used  in  testing  for  starch 
(Ex.  72  b). 

c.  To  the  test-tube  containing  water  and  iodine,  add  an  equal 
volume  of  carbon  disulphide  and  shake  (?). 

d.  Test  for  an  Iodide.    Take  a  crystal  of  potassium  iodide  m 
(color  ?)  and  dissolve  it  in  5  c.c.  of  water  (color  of  solution  ?).  • 
Add  2  c.c.  of  carbon  disulphide  and  shake  (?).    Why  is  not  the 
color  of  iodine  visible? 

Holding  the  tube  steady,  add  now  a  drop  or  two  of  chlorine- 
water,  and  observe  carefully  whether  the  color  appears  in  the  ^ 
carbon  disulphide  or  in  the  aqueous  layer  (?)  and  what  color  it  is 
(?).  Then  shake  vigorously  and  allow  the  mixture  to  settle. 
What  substance  has  been  liberated?  Write  the  equation  [205] 
(?).  To  what  variety  of  chemical  changes  does  this  one  belong? 

e.  Repeat  d,  using  bromine-water  instead  of  chlorine-water 

(?). 

/.  Summarize  the  properties  of  iodine:  color  of  solid  (?),  of 
vapor  (?),  density  of  vapor  compared  with  air  and  with  bromine 


50     COMPARISON  OF  THE  HALOGEN  COMPOUNDS 

vapor  (?),  density  of  solid  compared  with  water  (?),  solubilities 
in  four  solvents  (?). 

Compare  the  affinities  of  chlorine,  bromine,  and  iodine  for 
potassium  (?). 

EXERCISE  36 
COMPARISON  OF  THE  HALOGEN  COMPOUNDS 

Object:  To  learn  how  a  chloride,  a  bromide,  and  an  iodide  react  with 
sulphuric  acid,  and  to  observe  the  properties  of  the  hydrogen  com- 
pounds of  the  halogens. 

Apparatus:   Mortar.    Test-tubes.    Glass  rod. 

Materials:  Potassium  chloride.  Sulphuric  acid  (cone.).  Litmus 
paper  (blue).  Ammonium  hydroxide  (sol.).  Potassium  bro- 
mide. Potassium  iodide. 

Note :  Remember  that  the  hydrogen  compounds  of  the  halo- 
gens are  all  colorless. 

a.  Hydrogen  Chloride.    Pulverize  about  1  g.  of  potassium 
chloride  (color  ?),  place  it  in  a  test-tube,  and  add  0.5  c.c.  (not 
more)  of  concentrated  sulphuric  acid  (?). 

Blow  the  breath  across  the  mouth  of  the  tube  (?). 

Test  the  gas  with  moistened  blue  litmus  paper  (?).  )' 

Lower  into  it  a  glass  rod  dipped  in  ammonium  hydroxide 

solution,   which  will  give   off  ammonia  gas   (?).    Write  the 

equation  (?).     ^Vj&n  a\\l?$ 

b.  Is  any  colored  gas  visible  in  a?    Why  is  the  color  of  chlo- 
rine not  observable? 

c.  Hydrogen  Bromide.    Repeat  a  in  every  detail,  using  po- 
tassium bromide;  make  the  same  notes  (?)  and  answer  the  same 
questions  (?). 

d.  Is  there  a  colored  gas  or  vapor  visible  in  c?    Name  it  (?). 
How  could  you  distinguish  a  bromide  from  a  chloride? 

e.  Hydrogen   Iodide.    Repeat  a  in  every  detail,  using  po- 
tassium iodide,  make  the  same  notes  (?)  and  answer  the  same 
questions  (?). 

/.  Warm  the  tube  from  e  (?).  What  is  the  colored  vapor? 
Does  it  form  crystals  on  the  tube?  Stop  heating,  and  let  the 
vapor  condense.  What  gas  can  you  recognize  by  its  odor 
[CAUTION]? 


VALENCE  OF  A  METAL  BY  DISPLACEMENT      51 

Was  this  odorous  gas  formed  from  the  potassium  iodide  or  the 
sulphuric  acid  (in  answering,  consider  the  formulae  of  these  sub- 
stances and  of  the  gas)?  By  what  sort  of  chemical  action  must 
this  gas  have  been  formed?  Could  hydrogen  iodide  have  pro- 
duced such  an  action?  Write  an  equation  to  illustrate  your 
answer  (?).  Why,  then,  was  iodine  liberated? 

g.  Using  the  results  of  this  exercise,  how  could  you  recognize 
a  bromide  and  an  iodide,  and  distinguish  them  from  a  chloride? 

What  other  method  of  recognizing  bromides  and  iodides  did 
we  learn  before? 

EXERCISE  37 

VALENCE  OF  A  METAL  BY  DISPLACEMENT 

Object:  To  determine  (1)  the  weight  of  hydrogen  which  is  displaced 
by  one  at.  wt.  (24.32)  of  magnesium,*  and  (2)  the  valence  of  magne- 
sium. If,  e.g.,  24.32  g.  of  magnesium  is  found  to  displace  (and 
combine  in  place  of)  one  at.  wt.  (1.008  g.)  of  hydrogen,  the  atomic 
weight  of  magnesium  is  univalent.  If  it  displaces  two  at.  wts.  of 
hydrogen  (2.016  g.),  it  is  bivalent,  and  so  forth  (quantitative). 

FIRST  METHOD 
Apparatus:  Balance.     200  c.c.  flask.     Stopper  (1-hole).     L-tube 

and  rubber  delivery  tube.     2-liter  (or  1-liter)  bottle  and  glass 

plate  or  cork.     Trough.     50  c.c.  graduated  cylinder.     Funnel. 

Thermometer.    Barometer.    500  c.c.  graduated  cylinder  (1  for 

10  pupils). 
Materials:   Magnesium  wire  (2  mm.  diam.),  or  iron  piano-wire,  or 

aluminium  wire.      Hydrochloric  acid  (pure,  cone.). 

a.  Take  a  piece  of  magnesium f  wire  weighing  about  1.7  g. 
and  determine  (balance)  its  exact  weight  to  the  nearest  centi- 
gram (?) ;  tabulate  the  data  as  shown  under  d. 

Fit  the  200  c.c.  flask  with  a  one-hole  stopper,  L-tube,  and 

*With  another  metal  the  same  directions  and  questions  apply  ^ 
provided  only  the  name  of  the  metal  be  substituted  for  that  of  mag- 
nesium throughout,  and  the  appropriate  atomic  weight  (iron,  55.84; 
aluminium,  27.1)  is  employed  in  the  statement  of  the  object  and  in  d 
and  e.  If  one  method  only  is  used,  try  the  third. 

t  Other  metals,  such  as  aluminium  (wire,  about  1.4  g.),  may  be 
used. 


52       VALENCE  OF  A  METAL  BY  DISPLACEMENT 

rubber  delivery  tube,  and  test  for  air-tightness  (Ex.  7  d).  Fill 
the  2-liter  bottle*  with  water  and  invert  it  on  the  support  in  the 
trough.  Place  in  the  500  c.c.  graduated  cylinder  20  c.c.  of  con- 
centrated hydrochloric  acid  and  dilute  to  200  c.c.  with  water. 
Set  the  funnel  in  the  flask,  and  pour  into  it  the  acid  from  the 
graduated  cylinder.  In  removing  the  funnel,  be  careful  not  to 
wet  the  neck  of  the  flask  with  the  acid. 

Coil  up  the  magnesium  wire  so  that  it  can  be  pushed  into 
the  neck  of  the  flask,  when  the  latter  is  held  in  an  inclined 
position.  The  coil  must  be  so  large  that  the  wire  sticks  in  the 
neck  of  the  flask  and  does  not  slide  into  the  acid.  Replace  the 
stopper  in  the  flask  and  insert  the  delivery  tube  into  the  mouth 
of  the  2-liter  bottle.  Now,  shake  the  flask  slightly  so  as  to  bring 
the  acid  in  contact  from  time  to  time  with  the  metal.  When  the 
wire  falls  into  the  acid,  place  the  body  of  the  flask  immediately 
in  the  water  in  the  trough.  This  will  tend  to  keep  the  acid  cool, 
and  prevent  the  heat  of  the  reaction  from  raising  the  tempera- 
ture of  the  acid  and  causing  the  action  to  proceed  too  rapidly. 
When  the  magnesium  has  all  disappeared,  remove  the  delivery 
tube. 

b.  Lower  the  bottle  in  the  trough  (adding  water,  if  necessary) 
until,  on  looking  horizontally,  with  the  eye  at  the  level  of  the 
water,  the  levels  inside  and  outside  are  seen  to  be  the  same. 
Incline  the  bottle,  if  necessary,  to  accomplish  this.    While  the 
bottle  is  in  this  position,  cover  the  mouth  with  a  glass  plate  (or 
insert  a  cork),  and  set  the  bottle  with  its  contents  erect  upon  the 
table. 

Read  the  temperature  of  the  water  (?).  Ascertain  also  the 
height  of  the  barometer  (?). 

If  there  is  not  time  to  proceed  with  the  operations  directed 
below,  the  bottle  and  its  contents  may  be  set  aside  until  the 
following  period. 

c.  The  weight  of  this  hydrogen  is  to  be  found,  not  by  weighing 
it  ourselves,  but  by  measuring  its  volume,  and  using  the  fact 
that  22.4  liters  of  the  dry  hydrogen  at  0°  and  760  mm.  weigh 
2.016 g.  (seed). 

*  A  1-liter  bottle  (or  1-1.  graduated  cylinder)  if  available  is  better, 
because  about  0.9  g.  of  magnesium  (or  1.8  g.  of  iron,  piano-wire,  or 
0.7  g.  of  aluminium  wire)  and  8  c.c.  of  the  acid  diluted  to  100  c.c.  are 
then  used  and  time  is  saved. 


VALENCE  OF  A  METAL  BY  DISPLACEMENT      53 

d.  Use  a  graduated  cylinder  (500  c.c.)  to  fill  the  bottle  once 
more  to  the  top  with  water,  noting  carefully  the  volume  of  water 
required  (?). 

The  hydrogen  was  mixed  with  water  vapor.  Find  the  ten- 
sion of  the  aqueous  vapor  at  the  temperature  recorded  in  a 
[Appendix  I]  (?)  and  subtract  this  from  the  barometric  height 

(?)• 

Reduce  the  volume  of  hydrogen,  from  the  observed  tempera- 
ture and  barometric  pressure  as  just  corrected,  to  0°  and  760 
mm.  (?). 

Calculate  the  weight  of  this  hydrogen.  22.4  liters  weigh 
2.016  g. 

Weight  of  metal  taken  g. 

Volume  of  hydrogen  obtained  c.c. 

Temperature 

Barometric  height  mm. 

Tension  of  aqueous  vapor  mm. 

Pressure  of  hydrogen,  corrected  mm. 

Volume  of  hydrogen  at  0°  and  760  mm.  c.c. 

Weight  of  this  hydrogen  g. 

e.  The  atomic  weight  of  magnesium  is  24.32.     State  just  what 
experimental  fact  this  sentence  represents  (?). 

/.  The  weight  of  hydrogen  found  in  d  was  that  displaced  by 
the  weight  of  magnesium  taken  in  a.  Calculate  from  these  data 
the  weight  of  hydrogen  which  would  be  displaced  by  one  atomic 
weight  (24.32  g.)  of  magnesium  (?).  What  is  the  nearest  whole 
number  of  atomic  weights  of  hydrogen  (1.008  g.)  contained  in 
this  weight  of  hydrogen?  This  whole  number  is  the  valence  of 
magnesium.  Mg  therefore  displaces  xR.  Supply  the  value  you 
have  found  for  x  (?). 

g.  How  many  formula  weights  of  hydrochloric  acid  (HC1) 
are  required  to  furnish  this  amount  of  hydrogen?  Now  make 
the  complete  equation,  supplying  the  values  you  have  found 
for  x,  y  and  z: 

Mg  +  2/HC1  — >  MgCl2  +  zH. 

You  did  not  measure  the  weight  of  C12,  or  determine  the  value 
of  z.  What  law  of  chemistry  enables  you  to  supply  this  value 
without  measurement? 


54       VALENCE  OF  A  METAL  BY  DISPLACEMENT 


h.  If  hydrogen  is  univalent,  what  is  the  valence  of  oxygen  in 
water  (H2O)?  Write  the  formula  of  magnesium  oxide  (?). 

j.  If  the  formula  of  hydrogen  sulphide  is  H2S,  what  is  the 
formula  of  magnesium  sulphide? 

SECOND  METHOD 

Apparatus:  Wide  test-tube  with  2-hole  stopper  to  fit.  Funnel. 
Pinch-clamp,  rubber  connection  and  glass  tubing.  Rubber  de- 
livery tube.  Iron  stand,  ring,  and  clamp.  1-liter  bottle.  Trough. 
Thermometer.  Barometer.  500  c.c.  graduated  cylinder. 

Materials:  Magnesium  ribbon,  or  iron  piano-wire,  or  aluminium 
wire,  or  zinc  (C.P.  gran.).  Hydrochloric  acid  (pure,  cone.). 

a.  Take  a  piece  of  magnesium  ribbon  weighing  about  0.9  g.* 
and  determine  (balance)  its  exact  weight  to  the  nearest  centi- 
gram (?).    Tabulate  all  data  as  shown  under  d 
(First  Method). 

Fit  a  wide  test-tube  with  a  2-hole  stopper, 
straight  tube  reaching  almost  to  the  bottom, 
funnel,  pinch-clamp,  and  short  rubber  connec- 
tion. Set  this  up  as  in  Fig.  16,  using  the  tri- 
angle on  a  ring  to  support  the  funnel,  and  a 
clamp  to  hold  the  test-tube.  The  L-tube  must 
not  project  below  the  bottom  of  the  stopper. 
Test  for  air-tightness  (Ex.  7  d). 

Coil  up  the  magnesium  ribbon,  place  it  in  the 
test-tube,  and  replace  the  stopper,  Through 
the  funnel,  fill  the  apparatus  completely,  from 
the  tip  of  the  delivery  tube  to  the  clamp  below  the 
funnel,  with  water.  Close  the  clamp  when  the 
funnel  has  almost  emptied  itself.  Invert  the 
1-liter  bottle  (or  a  1-liter  graduated  cylinder), 
filled  with  water,  on  the  support  in  the  trough,  and  insert  the 
delivery  tube  in  the  mouth  of  the  bottle. 

*  For  a  2-liter  bottle,  take  1.8  g.  of  magnesium.  For  other  metals 
(and  1-liter  bottle)  use  iron  (piano-wire,  about  0.9  g.),  aluminium 
(wire,  about  0.7  g.),  or  zinc  (pure,  granulated,  about  1  g.).  If  zinc 
is  used,  weigh  the  test-tube  first  empty  and  again  with  the  zinc, 
getting  the  weight  of  the  latter  by  difference:  also  coil  the  platinum 
wire  and  place  it  amongst  the  zinc  (the  glass  rod  need  not  be  de- 
tached). 


FIG.  16 


VALENCE  OF  A  METAL  BY  DISPLACEMENT      55 

Fill  the  funnel  with  pure,  concentrated  hydrochloric  acid, 
and  admit  this  to  the  test-tube,  a  little  at  a  time,  in  such  a  way 
that  a  steady,  rapid,  but  not  violent  action  takes  place.  Re- 
plenish the  funnel,  if  necessary,  so  that  the  funnel  never  becomes 
entirely  empty.  A  good  deal  of  the  acid  may  be  required  at 
first  (especially  with  other  metals  than  magnesium),  before 
sufficiently  rapid  action  sets  in.  When  the  metal  has  all  dis- 
appeared, drive  all  the  gas  over  into  the  bottle  by  pouring  water 
once  more  through  the  funnel  (be  careful  that  no  air  is  carried 
in  with  the  water). 

b  toj.    Follow  the  directions  given  under  the  First  Method. 

THIRD   METHOD 

(Easily  applicable  to  magnesium  only) 

Apparatus:  Balance.  250  c.c.  bottle.  Trough  (stone  ware  or 
enamelled).  50  c.c.  graduated  cylinder.  Glass  plate.  Ther- 
mometer. Barometer. 

Materials:   Magnesium  ribbon.    Hydrochloric  acid  (cone.). 

a.  Weigh  (balance)  to  the  nearest  centigram  exactly  2  meters 
of  magnesium  ribbon  (?).  Calculate  what  length  will  weigh 
exactly  0.2  g.  and  cut  off  this  length  for  use.  Record  all  data  as 
shown  under  d  (First  Method).  Roll  the  ribbon  into  a  spiral 
coil  somewhat  smaller  than  the  inside  diameter  of  the  mouth  of 
the  250  c.c.  bottle. 

Place  in  the  trough  about  5  cm.  depth  of  water.  Measure 
into  the  bottle  30  c.c.  of  hydrochloric  acid  (cone.)  and  fill  it  up 
to  the  brim  with  water.  Cover  it  with  a  glass  plate  and  invert 
it  in  the  trough,  leaving  the  glass  plate  in  the  trough  with  the 
bottle  inverted  upon  it.  If  any  air  gets  into  the  bottle,  lift  out 
the  bottle  with  the  plate  firmly  pressed  against  the  mouth,  fill 
it  up  with  water  and  try  again. 

Place  the  spiral  of  magnesium  ribbon  in  the  trough  and  slip 
the  mouth  of  the  bottle  over  it,  setting  the  bottle  down  firmly  on 
the  bottom  of  the  trough.  When  the  magnesium  has  all  dis- 
appeared, slide  the  bottle  back  on  to  the  glass  plate. 

b  to  j.  Follow  the  directions  given  under  the  First  Method. 


56  SALTS 

EXERCISE  38* 

SALTS 

Object:  To  prepare  lists  of  the  three  ways  of  liberating  elements 
and  the  six  ways  of  preparing  salts  which  have  been  met  with 
during  the  preceding  work. 

Apparatus:  Test-tubes.    Trip  scales.    Watch  glass.     Becker. 

Materials:  Magnesium  ribbon.  Sulphuric  acid  (dil.).  Sodium 
carbonate.  Calcium  chloride. 

a.  Put  5  cm.  of  magnesium  ribbon  in  dilute  sulphuric  acid 
in  a  test-tube  (?).    What  is  the  gas  given  off?    What  other 
product  is  formed  and  how  should  you  obtain  it  in  solid  form? 
Write  the  equation,  assuming  Mg  to  be  bivalent  (?).     Write 
an  ionic  equation  also  (?).    Which  of  the  varieties  of  chemical 
change  is  here  illustrated? 

Give  two  other  ways  of  liberating  an  element,  with  one  illus- 
tration of  each  (?). 

b.  Place  2  g.  of  sodium  carbonate  in  one  test-tube  and  1  g. 
of  calcium  chloride  in  another.    Dissolve  each  salt  in  10  c.c.  of 
water.    Heat  the  calcium  chloride  solution  to  boiling  and  add 
to  it  a  little  sodium  carbonate  solution  (?).    Shake,  wait  until 
the  precipitate  has  settled,  and  add  one  more  drop  of  the  sodium 
carbonate  solution.     Continue  the  three  operations  described 
in  the  last  sentence  until  the  last  drop  produces  no  further  pre- 
cipitation in  the  clear  part  of  the  liquid.    Then  filter  the  mixture 
and  evaporate  two  or  three  drops  of  the  clear  filtrate  in  a  watch 
glass  as  in  Ex.  10/(?). 

Write  the  formulae  of  the  two  salts  taken  (?).  Separate  the 
radicals  in  brackets  thus  (NH4)  (N03).  Complete  the  equation 
as  a  double  decomposition  (?).  Write  the  names  under  the 
formulae  of  the  products  (?).  Write  the  equation  in  ionic  form 
also  (?). 

Define  each  of  the  two  ways  of  forming  salts  which  are  illus- 
trated in  this  experiment  (?).  Define  a  third  way  used  in 
Ex.  23  e,  f.  What  have  these  three  ways  in  common?  Define  a 
fourth  way  met  with  in  Ex.  38  a  (?).  Define  a  fifth  way  which 
was  illustrated  in  Ex.  5  dt  Ex.  16  (?).  Define  a  sixth  way  illus- 
trated in  Ex.  6  c. 

*  Exercises  38  and  39  are  placed  here  as  part  of  the  review  follow- 
ing Chap.  XVIII.  If  more  convenient,  they  may  precede  Ex.  25. 


HYDROGEN  PEROXIDE  57 

EXERCISE  39 
CHEMICAL  EQUILIBRIUM  IN  DOUBLE  DECOMPOSITION 

Object:  To  study  a  reversible  action,  to  show  that  it  is  incomplete, 
and  to  try  one  of  the  ways  of  carrying  such  a  reaction  to  completion. 
[Read  235.] 

Apparatus:  Test-tubes. 

Materials:  Ammonium  thiocyanate.    Ferric  chloride. 

a.  When  solutions  of  two  substances,  each  composed  of  two 
radicals,  are  mixed,  and  no  precipitate  is  observed,  interaction 
nevertheless  occurs  [174]. 

Place  10  c.c.  of  water  in  each  of  two  test-tubes,  add  to  one 
a  single  drop  of  ammonium  thiocyanate  solution,  and  to  the 
other  a  single  drop  of  ferric  chloride  solution.  Now  mix  the 
solutions  (?).  The  radicals  are  (NH4)(CNS)  and  (Fe)(Cl),. 
Write  the  equation  for  the  action  which  may  be  assumed  to  have 
occurred.  Is  there  any  evidence  that  interaction  has  taken 
place?  Which  of  the  four  is  the  colored  substance?  Use  the 
mixture  for  b. 

b.  When  no  precipitate  is  formed,  is  an  action  like  the  above 
complete?    To  answer  this  question,  divide  the  mixture  from  a 
equally  between  four  test-tubes.    Keep  one  for  reference.     To 
the  second  add  one  drop  of  ferric  chloride  solution  (?),  and  to 
the  third  a  drop  of  ammonium  thiocyanate  solution  (?).    In- 
terpret the  result.    Now  add  to  the  fourth  tube  a  few  drops  of 
ammonium  chloride  solution  (?)  and  explain. 

What  other  action  have  we  shown  to  be  reversible  [127]?  All 
double  decompositions  of  substances  composed  of  radicals  are 
reversible,  like  these  two.  They  are  also  often  far  from  com- 
plete, when,  as  in  the  present  instance,  precipitation  does  not 
occur.  Why  does  precipitation  tend  to  make  the  action  more 
nearly  complete? 

EXERCISE  40 
HYDROGEN  PEROXIDE 

Object:  To  prepare  a  solution  of  hydrogen  per oxide ,  to  observe  its 

properties,  and  to  try  a  delicate  test  for  its  presence. 
Apparatus:   Glass  rod.    Flask.    Test-tubes.     Funnel 


58  HYDROGEN  PEROXIDE 

Materials:  Sodium  peroxide  (powdered).  Litmus  papers.  Sul- 
phuric acid  (dil.).  Manganese  dioxide.  Splints.  Lead  nitrate 
(sol.).  Ammonium  sulphide  (sol.).  Filter  paper.  Potassium 
dichromate  (sol.).  Ether. 

a.  To  prepare  a  solution  of  hydrogen  peroxide,  take  100  c.c. 
of  cold  water  in  a  flask,  and  about  1  c.c.  of  pulverized  sodium 
peroxide  on  a  piece  of  paper.    Add  the  peroxide  to  the  water, 
a  very  little  at  a  time,  shaking  and  cooling  the  mixture  in  running 
water  during  the  process. 

Test  a  drop  of  the  solution  on  litmus  papers  (?).  Now,  while 
still  shaking  and  cooling  in  the  same  way,  add  dilute  sulphuric 
acid  a  few  drops  at  a  time,  until  the  mixture  is  acid.  Write  the 
equation  (?).  What  does  the  solution  now  contain? 

b.  Take  15-20  c.c.  of  the  solution  in  a  test-tube,  and  place 
about  1  c.c.  of  pulverized  manganese  dioxide  on  a  piece  of  paper. 
Light  a  wooden  splint,  throw  the  manganese  dioxide  into  the 
solution  (?),  and  test  the  gas  in  the  tube  for  oxygen  (?).    Write 
the  equation   (?).    The  manganese  dioxide   (catalyst)   is  un- 
changed.   Is  hydrogen  peroxide  stable  or  not? 

c.  Take  2  drops  of  lead  nitrate  solution  Pb(N03)2,  dilute 
with  5  c.c.  of  water  and  add  2  drops  of  ammonium  sulphide 
solution  (NH4)2S  (?).    Pour  the  mixture  on  to  a  filter.    The 
precipitate  is  lead  sulphide,  formed  by  double  decomposition. 
Write  the  equation  (?).    Wash  the  precipitate  and  whole  filter 
paper  with  water  and,  when  the  water  has  run  through,  wash 
once  more.    Then  pour  upon  the  precipitate  some  of  the  hy- 
drogen  peroxide  solution  [222]   (?).     Write  the  equation  (?). 
To  what  class  of  substances  does  hydrogen  peroxide  here  show 
itself  to  belong? 

d.  Test  for  Hydrogen  Peroxide.    Take  about  1  c.c.  of  potas- 
sium dichromate  solution  and,  to  liberate  dichromic  acid,  add 
an  equal  volume  of  dilute  sulphuric  acid.    Take  now  a  portion 
of  the  hydrogen  peroxide  solution,  add  2-3  c.c.  of  ether,  close 
with  the  thumb  and  shake.     Then  add  to  it  one  drop  of  the 
solution  containing  dichromic  acid  and  shake  again  [223]  (?). 

e.  Summarize  the  observed  properties  of  hydrogen  peroxide: 
color  (?),  solubility   (?),  stability  (?),  oxidizing  or  reducing 
action  (?),  test  (?). 


FORMS  OF  SULPHUR  59 

EXERCISE  41 
HYPOCHLOROUS  ACID.    BLEACHING 

Object:  To  find  out  how  the  commonest  "bleach"  does  its  work,  and 

what  kind  of  substances  it  bleaches. 
Apparatus:   90  c.c.  generating  bottle,  2-hole  stopper,  thistle,  L-, 

and  delivery  tubes.     Funnel.     Test-tubes. 

Materials :  Bleaching  powder.  Filter  paper.  Marble  (chips) .  Litmus 
papers.   Colored  calico  (small  strips).   Hydrochloric  acid  (dil.). 

a.  Take  about  2  c.c.  of  bleaching  powder  with  20  c.c.  of  water 
in  a  test-tube,  shake  from  time  to  time  and  finally  filter  to 
obtain  a  clear  solution.     Meanwhile  arrange  an  apparatus  to 
generate  carbon  dioxide  as  in  Ex.  59  a.    Pour  most  of  the  clear 
bleaching  powder  solution  into  another  test-tube,   and  pass 
carbon  dioxide  through  it  for  5  minutes.    The  precipitate  is 
calcium   carbonate   CaC03.    Filter   again,   to   obtain   a   clear 
solution  of  hypochlorous  acid  [226]  for  use  in  c. 

b.  In  the  rest  of  the  bleaching  powder  solution  dip  strips  of 
litmus  paper.     Leave  one  in  the  solution  (?).     Does  bleaching 
powder  solution  bleach?    Hang  the  other  in  the  air  (?).    What 
acid  here  liberates  the  hypochlorous  acid?    To  what  class  of 
chemical  actions  does  that  on  the  litmus  belong? 

c.  In  the  hypochlorous  acid  solution  from  a  place  small  pieces 
of  (1)  litmus  paper,  (2)  paper  with  printing  on  it  [356],  (3)  paper 
with  writing  in  ink  [499]  and  (4)  in  pencil  [330],  and  (5)  colored 
calico.    Observe  and  record  the  effect  on  each  (?).    Which  of 
these  owe  their  color  or  blackness  to  free  carbon,  and  which  to 
colored  organic  compounds?    Does  hypochlorous  acid  oxidize 
free  carbon?    What  does  it  oxidize? 

EXERCISE  42 
FORMS  OF  SULPHUR 

Object:   To  study  a  substance  which  shows  two  solid  forms  and   two 

liquid  forms. 
Apparatus:  Test-tubes.     Mortar.     Watch  glass.     Lens  (1  for  10 

pupils).     Trough.     Funnel. 
Materials:  Sulphur  (roll).     Carbon  disulphide.     Filter  paper. 

a.  Rhombic  Sulphur.     Place  about  0.5  c.c.  of  powdered  roll 
sulphur  in  a  dry  test-tube,  add  2  c.c.  of  carbon  disulphide  and 


60  FORMS  OF  SULPHUR 

shake  (?).    Pour  the  solution  into  a  watch  glass  and  set  it  to 
evaporate  away  from  all  flames. 

Examine  the  crystals  with  the  eye  and  with  a  lens  and  make 
a  drawing  of  two  of  them  (?).  Are  they  brittle  or  soft?  Color? 
Are  they  transparent?  After  24  hours  (or  more),  are  they  still 
transparent? 

b.  Monoclinic  Sulphur.     Fold  a  filter  paper  as  if  for  filtration, 
and  put  water  in  the  trough.    Half  fill  a  dry  test-tube  with  roll 
sulphur.    Hold  the  test-tube  with  the  clamp  from  the  iron  stand 
and  melt  the  sulphur.    Heat  gently,  turning  the  tube  in  the 
flame.    Dark  brown  patches  show  overheating  at  these  points  — 
melted  sulphur  is  pale  straw-color. 

Hold  the  filter  paper  by  the  edge  at  the  three-fold  side  and 
pour  the  melted  sulphur  into  it.  Watch  the  crystals  grow. 
When  crystals  have  formed  at  the  surface  and  reached  the  center, 
pour  the  remaining  liquid  sulphur  promptly  into  the  trough  of 
water,  and  open  up  the  paper  immediately. 

Examine  the  crystals  with  the  eye  and  with  the  lens  and  make 
a  drawing  of  two  of  them  (?).  Are  they  brittle  or  soft?  Color? 
Are  they  transparent?  After  24  hours  (or  more),  are  they  still 
transparent?  If  not,  into  what  form  of  sulphur  have  they 
turned? 

Examine  the  part  that  was  poured  into  water.  Is  it  brittle 
or  soft?  Dry  a  small  piece  of  it  and  shake  it  with  1  c.c.  of  car- 
bon disulphide  (?). 

c.  Amorphous  Sulphur.    Half  fill  the  same  test-tube  with 
roll  sulphur  and  melt.    Continue  heating  until  the  sulphur  boils 
and  note  the  changes  in  color  and  fluidity  which  occur  (?).     If 
the  vapor  catches  fire,  allow  it  to  burn. 

Pour  the  boiling  sulphur  into  the  trough  of  water,  moving  the 
tube  about. 

Examine  the  product.  Is  it  crystalline?  Is  it  brittle  or  soft? 
Is  it  transparent?  After  24  hours  (or  more)  is  it  still  trans- 
parent? After  24  hours  (or  more),  dry  a  part  of  it  and  shake 
with  a  little  carbon  disulphide  (?).  To  find  out  whether  any 
has  dissolved,  pour  part  of  the  liquid  on  to  a  filter,  catch  a  few 
drops  of  the  filtrate  on  a  watch  glass,  and  allow  them  to  evapo- 
rate (?). 

What  is  the  insoluble  material?  Color?  Examine  with  a 
lens  (?).  Is  it  crystalline? 


HYDROGEN  SULPHIDE  61 

EXERCISE  43 

SULPHIDES  OF  METALS 

Object:   To  observe  the  activity  of  sulphur  towards  metals. 
Apparatus:  Test-tubes.     Mortar. 

Materials:  Sulphur  (roll).  Copper  foil  (strips).  Iron  (powder). 
Mercury  (dropper  in  bottle). 

a.  Place  about  2  c.c.  of  roll  sulphur  in  a  dry  test-tube  and 
fasten  the  tube  upright  in  the  clamp  on  the  stand.     Boil  the 
sulphur  and  then  drop  into  the  tube  a  strip  of  copper  foil  (?). 
Does  the  temperature  of  the  copper  change  noticeably?    Was 
it  heated  thus  by  the  flame,  the  sulphur  vapor,  or  what? 

Remove  the  strip  of  copper  and  describe  the  properties  of  the 
product  (?).  Name  it  (?)  and  write  the  equation  (?). 

b.  Mix  thoroughly  1   c.c.  of  iron  powder  with  1.5  c.c.  of 
powdered  roll  sulphur.    Place  the  mixture  in  a  test-tube  and 
clamp  the  latter  on  the  stand.    Heat  the  lower  part  of  the 
material  and,  when  the  reaction  begins,  withdraw  the  flame. 

Was  the  temperature  at  any  time  higher  than  that  which  the 
flame  could  have  produced?  What  was  the  source  of  the  heat? 

Describe  the  product  when  cold  (?).  Name  it  (?),  and  write 
the  equation  (?).  Keep  it  for  use  in  Ex.  44  e. 

c.  With  a  dropper  place  a  single  globule  of  mercury  in  the 
mortar.    Add  an  equal  volume  of  sulphur  and  rub  the  two  for 
several  minutes,  or  until  no  mercury  is  visible  (?).    Under  the 
same  conditions  (pressure,  temperature,  contact),  does  mercury 
combine  more  or  less  readily  with  sulphur  than  with  oxygen? 
Give  reasons  for  your  answer  (?). 

Does  sulphur  appear  to  have  about  the  same  activity  as  oxy- 
gen, or  much  more  or  much  less? 

EXERCISE  44 
HYDROGEN  SULPHIDE 

Object:  To  prepare  hydrogen  sulphide.  To  study  its  physical  and 
chemical  properties,  and  to  consider  uses  for  them. 

Apparatus:  Test-tube  with  1-hole  stopper,  L-tube,  and  rubber 
tubing.  Wide-mouth  bottle  and  glass  plate. 


62  HYDROGEN  SULPHIDE 

Materials:  Ferrous  sulphide  (small  lumps).  Hydrochloric  acid 
(da.)-  Litmus  papers.  Cupric  sulphate  (sol.).  Arsenious 
chloride*  (sol.).  Lead  nitrate  (sol).  Antimony  trichloride  (sol.). 

a.  Take  a  test-tube  fitted  with  a  1-hole  stopper,  L-tube,  and 
rubber  tube  ending  in  a  straight  glass  tube.    Hold  the  test-tube 
almost  horizontal  and  slip  into  it  carefully  about  3  c.c.  of  ferrous 
sulphide.    Add  dilute  hydrochloric  acid  and  replace  the  stopper. 
Note  the  color  (?)  and  odor  (?)  of  the  gas.    Avoid  breathing  it, 
however,  as  far  as  possible. 

b.  Fill  a  bottle  with  the  gas  by  upward  displacement  of  the 
air  and  cover  the  bottle  with  a  glass  plate. 

Set  fire  to  the  gas  at  the  end  of  the  delivery  tube.  Odor? 
What  products  are  formed?  Place  the  delivery  tube  in  a  test- 
tube  half  filled  with  water,  so  that  it  reaches  the  bottom  and  let 
the  gas  bubble  through  the  water  for  several  minutes.  Use  the 
solution  in  c. 

Now  set  fire  to  the  gas  in  the  bottle  (?).  What  products 
are  formed  when  the  gas  burns  in  a  bottle?  Why  is  the  result 
different  from  that  when  a  jet  of  the  gas  burned  in  the  air? 

When  the  solution  has  been  made,  pour  water  into  the  gen- 
erating tube  and  wash  it  out.  Put  solid  matter  in  the  jar  — 
not  in  the  sink. 

c.  Smell  the  solution  made  in  b  (?)  and  test  it  with  litmus 
paper  (?).     To  what  class  of  substances  does  hydrogen  sulphide 
belong?    What  other  name  is  given  to  the  solution? 

Take  4  test-tubes  and  in  each  place  about  2  c.c.  of  a  solution 
of  a  different  one  of  the  following  salts:  (1)  Cupric  sulphate,  (2) 
Arsenious  chloride  AsCl3,  (3)  Lead  nitrate  Pb(N03)2,  (4)  Anti- 
mony trichloride  SbCl3.  Add  a  part  of  the  solution  of  the  gas 
to  each  (?). 

What  variety  of  chemical  change  will  an  acid  and  a  salt 
undergo  in  solution  [173]?  Make  equations  for  the  four  actions 
accordingly  (?). 

d.  Summarize  the  observed  properties  of  hydrogen  sulphide 
(?).     How  could  you  identify  hydrogen  sulphide?    How  could 
you  use  it  in  identifying  the  metallic  radicals  in  different  salts? 

e.  To  the  residue  from  Ex.  43  b,  add  dilute  sulphuric  acid. 
Identify  the  gas  liberated,  using  at  least  three  different  proper- 
ties, and  record  the  results  (?). 

*  Dissolve  arsenic  trioxide  in  dilute  hydrochloric  acid. 


SULPHUR  DIOXIDE  63 

EXERCISE  45 

SULPHUR  DIOXIDE 

Object:   To  prepare  sulphur  dioxide  and  to  study  its  properties. 

Apparatus :  Watch-glass.  Platinum  wire.  Wide  test-tube,  2-hole 
stopper,  funnel,  pinchclamp,  rubber  and  glass  tubing.  Test- 
tubes..  Wide-mouth  bottle,  glass  plate  and  cork.  Trough. 

Materials:  Sulphur.  Sodium  bisulphite.  Hydrochloric  acid  (dil.). 
Pinks  or  grass  or  leaves.  Apple. 

a.  Place  on  a  watch-glass  a  particle  of  sulphur  and    touch 
it  with  a  warm  platinum  wire.     Bring  the  wire  with  the  ad- 
her  ing  sulphur  again  into  the  flame.    Withdraw  and  note  the 
color  (?)  of  the  flame  of  burning  sulphur  and  the  odor  (?)  of 
the  gas  produced.    Name  the  gas  that  has  this  odor  (?) ,  and  write 
the  equation  (?).  ~  «3  -:^ 

b.  Fit  up  an  apparatus  as  in  Fig.  16  (Ex.  37).  Place  in  the  test- 
tube  about  10  c.c.  of  sodium  bisulphite,  and  attach  a  straight 
glass  tube  reaching  down  to  the  bottom  of  an  upright,  dry  test- 
tube.    Put  dilute  hydrochloric  acid  in  the  funnel,  and  admit  it 
drop  by  drop  to  the  apparatus.     If  there  is  little  evidence  of 
action  (bubbling),  the  apparatus  may  be  warmed  very  slightly 
to  start  the  reaction. 

Put  water  in  the  trough.  Also  have  ready  a  bottle  contain- 
ing a  moist  pink  (or  some  grass  or  leaves)  and  half  a  slice  of  an 
apple.  Leave  the  other  half-slice  exposed  to  the  air  for  com- 
parison later.  Likewise  boil  half  a  test-tube  full  of  water  for 
2  minutes  and  set  aside  to  cool. 

c.  Now  transfer  the  delivery  tube  to  the  bottle,  and  close 
the  mouth   of  the  test-tube  firmly  with  the  thumb.     Pour 
quickly  a  little  water  into  the  test-tube  and  close  again  firmly. 
Still  keeping  the  thumb  in  position,  place  the  mouth  of  the  test- 
tube  under  the  water  in  the  trough.     Notice  the  level  of  the 
water  in  the  test-tube  and  then  remove  the  thumb  (?).     In- 
ference (?). 

d.  Cool  the  boiled  water  in  the  test-tube,  and  again  transfer 
the  delivery  tube,  inserting  it  to  the  bottom  of  boiled  water,  and 
let  the  gas  run  in  for  5  minutes.     Cork  this  tube  the  instant  the 
delivery  tube  is  taken  out,  so  as  to  enclose  the  gas,  and  not  admit 
air.    Keep  this  solution  for  Ex.  46. 


64  SULPHUROUS  ACID 

Cover  the  bottle  or,  better  still,  cork  it.  After  5  minutes, 
pass  more  of  the  gas  into  the  bottle,  and  finally  cork  it  again. 
Observe  the  color  of  the  contents  from  time  to  time  (?). 

Compare  the  pieces  of  apple  after  both  have  been  exposed  to 
the  air  for  a  day  or  more  (?). 

e.  Summarize  the  properties  of  sulphur  dioxide:  color  (?), 
odor  (?),  density  compared  with  air  [259]  (?),  solubility  (?), 
action  on  vegetable  coloring  matters  (?).  jju^^v^^ 

EXERCISE  46 
SULPHUROUS  ACID 

Object:   To  learn  the  properties  of  sulphurous  acid. 
Apparatus :   Evaporating  dish.     Test-tubes.     Mortar. 
Materials:  Sulphurous   acid   (from  Ex.   45  d).    Litmus  papers. 
Barium  chloride  (sol.).     Iodine. 

a.  Use  the  solution  made  in  Ex.  45  d.    Test  with  litmus 
papers   (?).    What  sort  of  substance  has  been  formed?    Is 
sulphur  dioxide  an  acidic  or  a  basic  oxide  [259]? 

b.  Pour  a  part  of  the  solution  into  an  evaporating  dish,  set 
it  on  the  wire  gauze,  and  boil  it  [HOOD],  noting  the  odor  from 
time  to  time  (?).     Is  sulphurous  acid  stable? 

c.  To  half  of  the  rest  of  the  solution  add  one  or  two  drops  of 
barium  chloride  solution  (?).     Disregard  any  very  slight  cloudi- 
ness. 

To  the  other  half  add  a  couple  of  crystals  of  iodine  (pul- 
verized in  the  mortar),  shake  until  the  iodine  has  dissolved, 
and  then  add  barium  chloride  solution  (?).  The  precipitate 
is  barium  sulphate  BaS04,  and  its  formation  shows  that  the 
radical  S03  has  become  S04. 

Which  substance  was  here  oxidized? 

What  substance  was  reduced?  Write  equations  for  the  action 
of  iodine  (?),  and  the  subsequent  action  of  barium  chloride  (?). 

d.  Summarize  the  properties  of  sulphurous  acid:    color  (?), 
odor  (?),  stability  (?),  oxidizing  or  reducing  agent  (?). 

If  the  water  for  the  solution  had  not  been  boiled,  what  would 
have  happened  [34,  par.  2]? 

How  should  you  prepare  a  solution  of  sodium  sulphite  from 
sulphurous  acid? 


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SULPHURIC  ACID  65 

EXERCISE  47 
SULPHURIC  ACID 

Object :   To  learn  the  properties  of  pure  and  of  diluted  sulphuric  acid, 

and  to  try  a  test  for  the  sulphate  ion. 

Apparatus:  Test-tubes.     Glass  rod.     Evaporating  dish. 
Materials:   Sulphuric     acid     (cone.).     Litmus     papers.     Barium 

chloride  (sol.).     Hydrochloric  acid  (cone.).     Sodium  sulphate. 

Copper  (shavings). 

a.  Take  5  c.c.  of  water  and  pour  into  it  about  1  c.c.  of  con- 
centrated sulphuric  acid  [CAUTION.     Never  pour  the  water  into 
the  acid].     Touch  the  back  of  the  hand  with  the  bottom  of  the 
test-tube  (?). 

b.  Apply  the  solution  with  a  glass  rod  to  litmus  papers  (?). 

c.  Boil  nearly  all  the  rest  of  the  solution  gently  in  an  evaporat- 
ing dish  with  a  small  flame  and  note  whether  there  is  any  odor. 
After  five  minutes,  test  again  with  litmus  papers  (?).     Is  the 
acid  like  sulphurous  acid,  or  is  it  more  stable  (?)?    Let  the  dish 
cool  before  washing  it  out. 

d.  Test  for  the  Sulphate  Ion  SO4  = .    To  the  remainder  of 
the  solution  add  barium  chloride  solution  (?).    Add  now  1  c.c. 
of  concentrated  hydrochloric  or  nitric  acid  (?).     Other  common 
salts  of  barium,  if  precipitated,  would  be  decomposed  and  dis- 
solved by  these  acids.    Write  the  equation  (?). 

Repeat  the  test,  using  a  few  particles  of  sodium  sulphate  or 
ammonium  sulphate  dissolved  in  water  (?).  Write  the  equa- 
tion (?). 

e.  Twist  a  few  copper  shavings  into  a  ball  and  place  them 
in  a  test-tube.    Add   1   c.c.   of  concentrated  sulphuric  acid. 
Heat  gently  with  a  small  flame.     Note  how  long  it  takes  to 
make  the  acid  hot  enough  to  interact  at  all  [CARE!     Hot  sul- 
phuric acid,  if  spilled,  may  produce  severe  burns].     Note  the 
odor  (?).     Test  to  see  whether  any  hydrogen  is  produced  (?). 
Has  the  sulphuric  acid  been  reduced?    What  sort  of  substance 
is  hot  concentrated  sulphuric  acid? 

/.  Summarize  the  properties  of  the  acid:  State  (?),  color  (?), 
odor  (?),  stability  (?),  action  on  litmus  (?),  action  on  water  (?), 
on  barium  chloride  (?),  on  elements  like  copper  (?). 


66 


PERCENTAGE  OF  OXYGEN  IN  AIR 


EXERCISE  48 
PERCENTAGE  OF  OXYGEN  IN  Am 

Object:  To  find  the  volume  of  oxygen  contained  in  a  definite  volume  of 
air  by  absorbing  the  oxygen  out  of  this  air  and  measuring  the 
shrinkage. 

Apparatus:  See  Fig.  17.  One  hole  in  the  cork  (better  than  rubber 
stopper,  because  latter  tends  to  slip  out  when  wet  with  the  alkali) 
is  plugged  with  a  bit  of  glass  rod  with  fire-polished  ends.  The 
lower  end  of  the  short  glass  tube  is  previously  heated  until  the 
opening  shrinks  to  half  its  original  diameter.  Graduated  cyl- 
inder. 

Materials:  Potassium  pyrogallate  (alkaline  sol.*).  Rubber  bands. 
Taper. 

a.  Before  attaching  the  funnel,  test  the  apparatus  (Fig.  17) 
for  air-tightness. 

Remove  the  test-tube,  temporarily,  and  take  the  glass  rod 
out  of  the  cork.  Pour  about  40  c.c.  of  the 
potassium  pyrogallate  solution  into  the  funnel. 
The  following  operations  must  be  done  quickly 
as  the  solution  gradually  absorbs  oxygen  from 
the  air  of  the  room  and  becomes  useless.  Do 
not  get  the  solution  on  the  hands,  as  it  stains 
the  skin. 

Open  the  pinchclamp  and  permit  the  liquid 
to  fill  the  rubber  tube  and  the  glass  tube  com- 
pletely down  to  the  opening  of  the  nozzle. 
Replace  the  test-tube,  fitting -the  cork  tightly 
into  its  mouth.  Finally,  close  the  hole  in  the 
cork  with  the  glass  rod,  thus  enclosing  a  volume 
of  air  equal  to  the  capacity  of  the  test-tube. 

Now,  open  the  pinchclamp.  A  few  drops 
of  the  solution  will  run  into  the  test-tube 
and,  as  the  oxygen  is  absorbed,  more  will 
follow.  Close  the  clamp  and  turn  the  test-tube  upside  down 
once  or  twice  to  bring  the  liquid  near  every  part  of  the  oxygen. 
In  doing  this,  hold  the  test-tube  with  a  folded  strip  of  paper 

*  For  20  students,  dissolve  200  g.  of  potassium  hydroxide  and  20  g. 
pyrogallic  acid  in  1  liter  water  immediately  before  use  and  keep 
tightly  stoppered. 


FIG.  17 


CARBON  DIOXIDE  IN  AIR  67 

(Fig.  1,  Ex.  1  a),  and  not  with  the  bare  hands,  since  this  would 
warm  the  gas  and  render  the  result  inaccurate.  Then  hold  the 
clamp  open,  invert  the  test-tube  and  hold  it  so  that  the  levels 
of  the  liquid  in  it  and  in  the  funnel  are  the  same,  and  close  the 
clamp. 

Restore  the  test-tube  to  its  original  position  and  place  on  it 
two  rubber  bands  to  mark  the  levels  of  the  lower  end  of  the 
stopper  and  the  surface  of  the  liquid. 

Light  a  taper,  disconnect  the  test-tube,  and  plunge  the  flame 
into  it  (?).  Without  disturbing  the  bands,  wash  the  test-tube 
out.  By  means  of  a  graduated  cylinder,  measure  and  record 
the  volumes  of  water  required  to  fill  the  test-tube  up  to  the 
lower  (?)  and  to  the  upper  (?)  bands.  The  former  is  the  volume 
of  the  oxygen,  the  latter  that  of  the  air. 

Calculate  the  percentage  of  oxygen  by  volume  in  air  as  follows: 

volume  of  oxygen  X  100 

— ; —    — r— : =  x  =  %  oxygen. 

volume  of  air 

What  gases  were  left,  after  the  oxygen  had  been  absorbed? 
What  properties  of  nitrogen  did  you  observe? 


EXERCISE  49 
CARBON  DIOXIDE  IN  AIR  AND  IN  THE  BREATH 

Object:   To  show  the  presence  of  carbon  dioxide  in  atmospheric  air 

and  in  expired  air. 
Apparatus:   Beaker.      Glass    tube.      Test-tube.      2    wide-mouth 

bottles  and  glass  plates.     Trough. 
Materials:   Barium  hydroxide  (sol).     Taper.    Lime  water. 

a.  Place  about  3  c.c.  of  clear  barium  hydroxide  solution  in 
the  bottom  of  a  clean  beaker  and  leave  it  exposed  to  the  air  for 
half  an  hour  or  more  (?).  Barium  hydroxide  Ba(OH)2  behaves 
towards  carbon  dioxide  like  limewater,  but,  being  more  soluble 
than  calcium  hydroxide,  its  solution  is  more  concentrated  and  a 
more  copious  precipitate  can  be  obtained.  Explain  the  result 
(?),  and  write  the  equation  for  the  action  (?). 

6.  Blow  air  from  the  lungs  through  a  straight  tube  into  5  c.c. 
of  limewater  (?). 

c.  Fill  two  bottles  with  water  and  invert  them  in  the  trough. 


68  AMMONIA 

By  means  of  a  tube,  fill  one  with  air  from  the  lungs  immediately 
after  drawing  a  breath.  Fill  the  other  with  air  after  the  lungs 
have  been  almost  emptied.  Slip  a  glass  plate  under  each  bottle 
and  set  both  upright  on  the  table.  Light  a  taper  and  plunge  it 
into  one  bottle  (?)  and  then  into  the  other  (?).  Explain  the 
result  (?). 

EXERCISE  50 
AMMONIA 

Object:    To  study  two  ways  of  obtaining  ammonia  and  to  observe  its 

physical  and  chemical  properties. 
Apparatus:   Test-tubes.     1-hole  stopper,  L-tube,  and  perforated 

cardboard.     2  wide-mouth  bottles,  and  glass  plates.     Glass  rod. 

Trough.     Beaker.     Cork. 
Materials:  Gelatine    (fine   flakes).    Litmus   papers.    Soda    lime. 

Ammonium     chloride.    Slaked    lime.    Ammonium    sulphate. 

Hydrochloric  acid  (cone.). 

a.  From  Organic  Matter.    Take  0.5  c.c.  of  gelatine  in  a  dry 
test-tube.    Place  moistened  litmus  papers  (blue  and  red)  in  the 
mouth  of  the  tube  and  heat  gently.    Note  the  odor  (?)  and  effect 
on  litmus  (?).     Insert  a  glass  rod  wet  with  concentrated  hydro- 
chloric acid  (?). 

Repeat,  first  mixing  on  paper  the  gelatine  with  an  equal 
amount  of  soda  lime  (?).  Almost  all  organic  compounds  con- 
taining nitrogen  give  ammonia  when  heated  with 
soda  lime,  and  this  is  therefore  a  test  for  such 
compounds. 

b.  From  an  Ammonium  Salt.    Place  a  little 
ammonium  chloride  in  the  palm  of  one  hand,  a 
little  slaked  lime  in  the  other,  and  rub  the  two 

together.    Note  the  odor  (?)  and  effect  on  mois-  * 

tened  litmus  paper  held  over  the  mixture  (?). 

Repeat,  using  ammonium  sulphate  and  slaked 
lime  (?). 

c.  Take  one-fourth  of  a  test-tube  full  of  am-        ^ 
monium  chloride  and  mix  it  on  paper  with  an        ^       jg 
equal  volume  of  slaked  lime.     Place  it  in  a  test- 
tube  provided  with  a  one-hole  stopper  and  L-tube  long  enough 
to  reach  the  bottom  of  the  inverted  bottle  (Fig.  18).    Clamp 


AMMONIA  69 

the  tube  so  that  the  mouth  is  inclined  very  slightly  down- 
wards (to  prevent  condensed  moisture  running  back).  Arrange 
the  perforated  card  on  a  ring,  and  first  slip  an  inverted  test- 
tube  over  the  L-tube.  Provide  a  test-tube  containing  a  few 
drops  of  concentrated  hydrochloric  acid.  Also,  place  water  in 
the  trough. 

Warm  the  mixture  very  gently  with  a  small  flame.  Dip  the 
end  of  a  thin  glass  rod  in  the  hydrochloric  acid,  and  bring  it 
close  to  the  perforation  in  the  card  to  ascertain  when  the  test- 
tube  is  filled  with  the  gas.  Dense  smoke  will  notify  you  of  this 
condition.  Remove  the  test-tube,  closing  it  firmly  with  the 
thumb,  and  with  the  other  hand  set  a  bottle  (to  be  used  in  e) 
over  the  L-tube. 

d.  Place  the  mouth  of  the  test-tube  under  water  and  remove 
the  thumb  (?).     Is  the  gas  soluble  in  water?    How  does  its 
behavior  compare  with  that  of  chlorine  (Ex.  21  a)  in  this  respect? 

e.  Warm  a  second  bottle  by  moving  it  rapidly  through  the 
flame.     Do  not  let  it  rest  in  the  flame  or  it  will  crack.    Place  in 
the  bottle  3  drops  of  concentrated  hydrochloric  acid,  cover  it 
with  a  glass  plate,  and  turn  it  so  as  to  spread  the  acid  as  com- 
pletely over  the  inner  surface  as  possible. 

Now,  ascertain  by  use  of  the  rod  dipped,  in  hydrochloric  acid 
whether  the  first  bottle  (c)  is  full  of  ammonia.  When  it  is,  raise 
it  off  the  tube,  slip  a  glass  plate  under  the  mouth,  and  set  the 
bottle  mouth  downwards  on  the  table  ready  to  be  used  in  g. 

f.  Swing  the  L-tube  downwards  so  that  its  free  end  is  just 
above  (but  not  touching!)  the  surface  of  the  5  c.c.  of  water  in 
the  bottom  of  a  beaker.    At  the  end  of  5  minutes  pour  the 
solution  into  a  test-tube,  cork  it  up,  and  reserve  for  use  in  Ex.  49. 
During  the  five  minutes  proceed  with  g,  but  swing  the  water 
round  hi  the  beaker  occasionally  to  submerge  the  surface  layer. 
Concentrated  ammonia  has  a  density  of  0.88,  i.e.,  1  c.c.  weighs 
0.88  g.    Will  the  solution  float  or  sink?    What  difference  would 
it  make  if  the  beaker  were  left  at  rest? 

g.  Bring  the  two  bottles  from  e  mouth  to  mouth  and  remove 
both  plates.     Invert  the  pair  of  bottles  once  or  twice  to  mix  the 
gases  (?).    What  is  the  deposit?    Describe  its  physical  proper- 
ties (?).    Write  the  equation  for  the  action  (?). 

h.  Summarize  the  observed  properties  of  ammonia  (?). 


T 


70        HYDROXIDE  AND  SALTS  OF  AMMONIUM 

EXERCISE  51 
HYDROXIDE  AND  SALTS  OF  AMMONIUM 

Object:  To  observe  the  properties  of  ammonium  hydroxide  and  of  salts 

of  ammonium,  and  to  learn  a  test  for  the  latter. 
Apparatus:  Glass  rod.    Evaporating  dish.     Beaker.    Test-tubes. 
Materials:  Litmus  papers.     Hydrochloric  acid  (dil.).    Ammonium 

chloride.     Sodium  hydroxide  (sol.).     Ammonium  sulphate. 

a.  Ammonium  Hydroxide.     Dip  a  rod  in  the  solution  made 
in  Ex.  50  /  and  touch  litmus  papers  with  it  (?).    To  what  class 
of  substances  does  the  material  in  solution  belong?    Write  the 
equation  for  the  formation  of  this  material  (?). 

b.  Pour  a  part  of  the  solution  into  an  evaporating  dish  and 
boil  it.    From  time  to  time  observe  its  odor  and  reaction  towards 
litmus  papers  (?),  proceeding  meanwhile  with  c.    What  must 
have  happened  to  the  compound  in  the  solution?    Is  it  a  stable 
or  an  unstable  compound  [304]?    Write  the  equation  (?).    Is 
this  action  a  reversible  one  or  not?    Is  it  complete? 

c.  Place  the  rest  of  the  solution  in  a  beaker,  add  dilute  hydro- 
chloric acid  a  little  at  a  time,  stirring  with  a  rod  and  testing  the 
liquid  on  litmus  papers  until  the  liquid  is  neutral.    Evaporate 
the  liquid  in  a  dish  almost  (but  not  quite)  to  dryness  (lower  the 
flame  towards  the  end),  allow  it  to  cool  and  describe  the  residue 
(?).    Write  the  equation  (?). 

d.  Summarize  the  properties  of  ammonium  hydroxide  (?) 

e.  Ammonium  Salts.      Place  not  over  0.2  c.c.  of  ammonium 
chloride  in  the  bottom  of  a  dry  hard  glass  test-tube.     Clamp  the 
latter  in  a  horizontal  position,  and  place  in  the  mouth  of  the 
tube  moistened  litmus  papers  (red  and  blue).    Heat  the  salt 
and  watch  the  test  papers  for  any  changes  and  describe  them  (?). 

Is  there  evidence  that  the  salt  decomposed?  What  were 
presumably  the  products?  Make  the  equation  (?).  Would 
these  products  recombine  (partially  at  least)  in  the  cool  part 
of  the  tube  (Ex.  50  #)?  Is  there  any  sublimate  vMble  (?)  and 
if  so,  what  is  it? 

What  would  be  the  final  effect  of  continuing  the  heating  of 
the  salt? 

/.  Test  for  Salts  of  Ammonium.  Take  2  c.c.  of  sodium  hy- 
droxide solution  and  add  a  few  particles  of  any  salt  of  ammonium 
(e.g.,  the  sulphate).  Warm,  and  observe  the  odor  (?). 


NITRIC  ACID  71 

Write  the  equation  as  a  double  decomposition   (?).    Which 
of  the  products  decomposes  to  give  the  ammonia? 


EXERCISE  52 
NITRIC  ACID 

Object:   To  prepare  nitric  acid,  to  study  its  properties,  and  iff  'ry  to 

test  for  a  nitrate. 
Apparatus:   Tubulated   retort    (glass  stopper).     Flask.     Trough. 

Funnel.     Porcelain  crucible. 
Materials:   Sodium    nitrate.     Sulphuric    acid    (cone.).     Charcoal 

(splinters).    Woolen  yarn  (white).    Copper  (shavings).    Splints. 

Zinc  (gran.).    Ferrous  sulphate  (sol.). 

a.  Put  about  20  g.  of  sodium  nitrate  in  a  tubulated  retort. 
Insert  the  neck  of  the  retort  into  the  mouth  of  a  flask  (Fig.  19). 
Clamp  the   tubulus    (mouth)   of 
the  retort  so  that  the  body  rests 
on  the  wire  gauze  and  the  flask 
is  partly  immersed  in  a  vessel  of 
cold  water.     Through  a  funnel  or 
thistle  tube  pour  about  15  c.c.  of 
concentrated  sulphuric  acid  upon  FIG.  19 

the    sodium    nitrate,    place    the 

stopper  in  the  tubulus  of  the  retort,  and  wait  until  the  acid 
has  moistened  the  entire  mass. 

Caution:  Sulphuric  acid  and  nitric  acid  both  produce 
severe  wounds  on  the  flesh  and  destroy  clothing.  The  nitric 
acid  to  be  prepared  is  100%,  and  the  greatest  care  must  be 
used  in  handling  it. 

Heat  the  retort  very  gently  [HOOD],  and  distil  at  as  low  a  tem- 
perature as  possible  until  no  more  nitric  acid  condenses  in  the 
neck  of  the  retort  (meantime,  proceed  with  d).  Allow  the  retort 
to  cool  before  touching  it.  What  is  the  brown  gas  seen  in  the 
retort  (?),  and  whence  does  it  come  [309]?  What  is  the  residue 
in  the  retort? 

6.  Pour  part  of  the  distillate  (nitric  acid)  into  the  porcelain 
crucible.  Does  its  vapor  produce  a  fog  with  moist  air  (breath)? 
Twist  an  iron  wire  round  a  splinter  of  charcoal,  set  fire  to  the 
latter,  and  dip  the  brightly  glowing  charcoal  into  the  acid  (?). 


72  NITRIC  OXIDE 

This  shows  its  oxidizing  power.    What  compound  of  carbon  is 
probably  formed? 

c.  Divide  the  rest  of  the  distillate  between  four  dry  test- 
tubes.    In  one  place  a  piece  of  white  woolen  yarn  (?),  in  the 
second  a  small  piece  of  copper  (?),  in  the  third  a  piece  of  a  splint 
(?),  and  in  the  fourth  a  small  piece  of  zinc  (?). 

The  action  on  copper  is  a  test  for  nitric  acid,  by  itself,  or  mixed 
with  other  substances. 

What  gas  does  zinc  displace  from  other  acids?  What  gas  is 
produced,  with  zinc,  here? 

d.  Test  for  the  (NO3)  radical  (follow  the  directions  with  care). 
Pour  into  a  test-tube  3  c.c.  of  ferrous  sulphate  solution.    Add 
to  it  2  drops  of  dilute  nitric  acid  and  shake.    Incline  the  tube 
very  slightly,  and  pour  concentrated  sulphuric  acid  (not  over 
2  c.c.)  in  a  steady  stream  down  the  wall  of  the  test-tube  so  that 
(being  a  heavy  liquid)  it  flows  to  the  bottom  and  collects  below 
the  ferrous  sulphate  solution  (?).    Describe  the  coloration  in 
the  layer  where  the  liquids  meet  (?). 

Repeat  the  test,  adding  a  small  crystal  of  sodium  nitrate, 
instead  of  the  nitric  acid,  and  shaking. 

How  should  you  recognize  an  unknown  substance  to  be  a 
nitrate? 

e.  Summarize  the  properties  of  nitric  acid  (?).  * 


EXERCISE  53 
NITRIC  OXIDE 

Object:  To  observe  the  action  of  dilute  nitric  acid  on  copper.  To 
prepare  nitric  oxide  and  study  its  properties.  To  observe  part  of 
the  process  used  in  the  fixation  of  atmospheric  nitrogen. 

Apparatus:  Gas  generating  bottle  (90  c.c.),  2-hole  stopper,  thistle, 
L-,  and  delivery  tubes.  Trough.  Wide-mouth  bottle.  Gradu- 
ated cylinder.  Test-tubes.  Deflagrating  spoon.  Glass  plate. 
Wide  test-tube,  2-hole  stopper,  dropper,  L-  and  delivery  tubes. 

Materials:  Copper  (shavings  or  clippings).  Nitric  acid  (cone.). 
Asbestos  paper.  Taper.  Phosphorus  (red).  Sodium  per- 
oxide. Litmus  papers. 

a.  Fit  up  a  generating  bottle  as  in  Fig.  10  (Ex.  10  a).    Place 
in  it  copper  shavings  or  clippings.     Invert  one  bottle,  one  test- J 


' 


s 


V 


NITRIC  OXIDE 


73 


tube,  and  the  graduated  cylinder,  all  full  of  water,  in  the  trough. 
Pour  some  water  through  the  thistle  tube,  and  an  equal  volume 
of  concentrated  nitric  acid  and  wait  for  the  action  to  start.  Then 
fill  the  bottle  and  test-tube  with  the  gas,  collect  about  30-50  c.c. 
(only)  of  the  gas  in  the  graduated  cylinder,  and  leave  them  stand- 
ing in  the  trough. 

Note  the  color  of  the  gas  in  the  generator  just  after  the  be- 
ginning of  the  action  (?)  and  again  later  (?). 

Note  also  the  color  of  the  liquid  in  the  generator.  This  is 
characteristic  of  cupric  salts,  and  is  the  color  of  the  cupric-ion 
Cu++ 

b.  What  is  the  color  of  the  gas?    Use  the  test-tube  full  of 
the  gas  to  test  its  solubility  in  water  as  in  Ex.  45  c  (?).    What 
happens  when  the  test-tube  is  opened  to  the  air  (this  action  is 
examined  further  in  d)l 

c.  Line  the  deflagrating  spoon  with  asbestos  paper  and  place 
in  it  a  little  red  phosphorus.     Cover  the  bottle  full  of  the  gas 
with  a  glass  plate,  and  set  it  upright  on  the  table.     Plunge  a 
burning  taper  into  the  gas  (?),  withdraw  it  instantly,  and  cover 
the  bottle.    Set  fire  to  the  phosphorus,  and  when 

it  is  burning  vigorously,  plunge  it  into  the  same 
bottle  (?). 

Heat  the  spoon  and  asbestos  paper,  to  burn  the 
adhering  phosphorus,  before  putting  the  spoon 
away. 

d.  Fit  a  wide  test-tube  with  a  2-hole  stopper, 
L-tube  and  rubber  delivery  tube,  and  a  dropper 
(Fig.  20).    Place  in  the  test-tube  about  1  c.c.  of 
sodium  peroxide.     Fill  the  dropper  with  water, 
and  immerse   the  delivery   tube  in  the  trough. 
Pinch  the  dropper  cautiously  so  as  to  allow  one 
drop  of  water  at  a  time  to  fall  on  the  peroxide. 
When  the  air  has  been  displaced  from  the  test- 
tube,  read  the  volume  of  the  gas  in  the  graduated  cylinder 
(?),  and  allow  the  oxygen  to  ascend,  a  few  bubbles  at  a  time, 
into  the  latter  (?).     Note  the  change  in  color  (?).     Slightly 
shake  the  water  in  the  cylinder  to  bring  it  in  contact  with  the  gas. 
Does  the  volume  change  (?)  and,  if  so,  in  which  direction?    Re- 
member that  oxygen  gas  is  being  added. 

Finally,  close  the  cylinder  with  a  glass  plate,  set  it  upright,  and 
test  the  water  in  it  with  blue  litmus  paper  (?). 


20 


74  NITROUS  OXIDE 

e.  Which  component  of  the  air  caused  the  nitric  oxide  to 
become  brown  in  6?  What  is  the  brown  gas?  What  property 
of  the  brown  gas  have  you  learned  in  dl  What  reaction  to  lit- 
mus had  the  water  in  the  cylinder  (?)  and  what  was  the  sub- 
stance formed  [312]?  What  great  industrial  process  is  based  on 
this  reaction  [313-4]? 

/.  Summarize  the  properties  of  nitric  oxide  (?). 

EXERCISE  54 
NITROUS  OXIDE 

Object:  To  prepare  nitrous  oxide  and  to  study  its  properties. 

Apparatus:  Test-tube,  1-hole  stopper,  L-  and  delivery  tubes. 
Test-tubes.  Wide-mouth  bottle.  Trough.  Deflagrating  spoon. 

Materials:  Ammonium  nitrate.  Splints.  Asbestos  paper.  Sul- 
phur. 

a.  Preparation  of  Nitrous  Oxide.  In  a  large  test-tube  pro- 
vided with  a  1-hole  stopper  and  rubber  and  glass  delivery  tube, 
place  10  g.  of  ammonium  nitrate.  Clamp  the  test-tube  at  an 
angle  of  45°.  Fill  one  bottle  and  two  test-tubes  with  water  and 
invert  them  in  the  trough  (use  warm  water,  if  available). 

Heat  the  nitrate  cautiously  but  continuously  with  a  small 
flame,  and  allow  the  gas  to  come  very  slowly.  If,  before  the 
vessels  are  filled  with  gas,  the  nitrate  threatens  to  give  out 
[explosion  possible],  first  remove  the  delivery  tube  from  the 
trough,  then  stop  heating,  and  add  more  ammonium  nitrate. 

Watch  the  water  in  the  delivery  tube.  Does  anything  else 
appear  to  be  produced  along  with  the  nitrous  oxide  gas?  What 
is  it? 

6.  Use  one  test-tube  of  the  gas,  as  in  Ex.  45  c,  to  find  out 
whether  the  gas  is  soluble  in  cold  water  (?).  Does  the  gas  differ 
from  oxygen  in  this  respect? 

c.  Into  the  second  test-tube  thrust  a  glowing  splinter  (?). 
Does  the  gas  differ  from  oxygen  in  this  respect? 

d.  Line  the  deflagrating  spoon  with  asbestos  paper  and  place 
on  it  a  little  sulphur.     Set  fire  to  the  sulphur,  without  heating 
the  spoon.     Immediately,  while  it  is  still  burning  feebly,  thrust 
it  into  the  bottle  of  the  gas  (?),  and  then  remove  it  and  cover  the 
bottle.    Heat  the  spoon  until  the  sulphur  burns  briskly  and 


PHOSPHINE  AND  PHOSPHORIC  ACID  75 

thrust  it  into  the  bottle  once  more  (?).  How  does  the  gas  differ 
in  behavior  from  oxygen? 

Note  the  odor  in  the  bottle  (?).  What  is  formed  when  sul- 
phur is  burned  in  nitrous  oxide? 

' e.  Summarize  the  properties  of  nitrous  oxide:  color  (?), 
solubility  (?),  density  compared  with  air  (?),  supports  com- 
bustion, how  well  (?). 

/.  Name  two  respects  in  which  nitrous  oxide  differs  from 
oxygen  (?).  When  nitrous  oxide  is  added  to  nitric  oxide,  no 
brown  gas  (Ex.  53  d)  is  formed:  this  is  another  difference. 


EXERCISE  55 
PHOSPHINE  AND  PHOSPHORIC  ACID 

Object:  To  prepare  phosphine  and  to  observe  the  reactions  of  phos- 
phoric acid  or  phosphates. 

Apparatus:  Test-tubes.    Glass-tubing.     Mortar.    Dropper. 

Materials:  Calcium  phosphide.  Litmus  papers.  Phosphoric  acid 
(sol.)  or  sodium  phosphate.  Ammonium  molybdate  (sol.*). 
Silver  nitrate  (sol.).  Ammonium  hydroxide  (sol.).  Nitric  acid 
(cone.). 

a.  Phosphine.  Drop  a  small  piece  of  calcium  phosphide, 
Ca3P2,  half  the  size  of  a  pea,  into  3  c.c.  of  water  in  a  test-tube  (?) . 
The  gas  is  phosphine  PH3.  Try  the  reaction  of  the  gas  (not  the 
liquid)  with  moist  litmus  papers  (?).  What  reaction  would 
ammonia  NHa  gas  give?  Note  the  odor  (?).  Is  the  gas  com- 
bustible? Is1  its  kindling  temperature  low  or  high? 

Test  the  reaction  of  the  water  (?).  What  must  the  dissolved 
substance  be?  Write  the  equation  for  the  action  of  the  calcium 
phosphide  on  water  (?). 

6.  Test  for  the  Phosphate  Radical.  To  10  c.c.  of  water  add 
not  over  1  c.c.  of  phosphoric  acid  H3P04  (or  0.5  c.c.  of  sodium 
phosphate).  Take  5  c.c.  of  ammonium  molybdate  solution, 
add  to  it  2  drops  (not  more,  reserve  the  rest  for  c)  of  the  phos- 
phoric acid  solution  and  warm  the  mixture  (?).  This  is  a  test 
for  the  radical  of  orthophosphoric  acid  (P04)  and  the  phosphates. 

*  70  g.  ammonium  molybdate  and  180  c.c.  nitric  acid  to  make  1 
liter  of  solution. 


76  ARSENIC  TRIOXIDE 

c.  To  the  rest  of  the  phosphoric  acid  solution  add  silver  nitrate 
solution,  shaking  and  adding  more  until  a  permanent  precipitate 
is  formed  (?).  The  precipitate  is  silver  orthophosphate  Ag3P04. 
Write  the  equation  (?). 

Like  all  double  decompositions,  this  one  is  reversible,  and  is 
therefore  incomplete.  Name  the  interacting  substances  in  the 
reverse  action  (?).  To  stop  this  reverse  action,  destroy  the  acid 
by  adding  ammonium  hydroxide  solution  one  drop  at  a  time, 
noting  the  effect,  shaking,  and  examining  again.  What  evidence 
is  there  that  the  action  now  goes  further  forward? 

Finally,  add  concentrated  nitric  acid  (?).  Which  way  does 
the  action  now  go? 

EXERCISE  56 
ARSENIC  TRIOXIDE 

Object:   To  observe  the  reduction  of  an  oxide  by  carbon  and  to  study 

the  properties  of  arsenic  trioxide. 
Apparatus :   Glass  tubing.    Test-tubes. 
Materials:  Arsenic  trioxide.     Charcoal  (powdered).     Hydrochloric 

acid  (cone.).     Sodium  hydroxide  (sol.). 

a.  Draw  out  a  piece  of  glass  tubing  to  make  two  ignition  tubes 
each  7  cm.  long.  Place  in  the  closed  end  of  one  a  very  small 
amount  of  arsenic  trioxide.  Heat  the  oxide,  and  watch  the  cold 
part  of  the  tube  for  a  sublimate  [324]  (?).  Is  the  oxide  volatile? 
Does  it  melt  before  vaporizing?  O^ 

6.  Place  a  small  amount  of  arsenic  trioxide  in  the  other  tube, 
and  above  it  a  little  powdered  charcoal.  Heat  the  oxide  and 
the  charcoal,  and  examine  the  cold  part  of  the  tube  [324]  (?). 
What  change  has  the  oxide  undergone? 

c.  Take  about  0.5  c.c.  of  arsenic  trioxide  in  a  test-tube,  add 
2  c.c.  of  water  and  warm  (?).    Now  add  1  c.c.  of  concentrated 
hydrochloric  acid  and  heat  again  (?).     To  what  class  of  oxides 
does  arsenic  trioxide  appear  to  belong?    Write  the  equation  (?). 
Set  aside  and  examine  later.     Is  the  action  reversible? 

d.  Take  about  0.5  c.c.  of  arsenic  trioxide,  add  2-3  c.c.  of 
sodium  hydroxide,  and  warm  (?).    To  what  class  of  oxides  does 
it  appear  now  to  belong? 


GRAPHITE  77 

EXERCISE  57 
GRAPHITE 

Object:  To  try  the  action  of  solvents,  and  of  solutions  of  acids  and 
bases  on  graphite,  to  see  whether  it  dissolves  in  the  former,  or  in- 
teracts with  the  latter. 

Apparatus:  Test-tubes. 

Materials:  Graphite  (powdered).  Hydrochloric  acid  (dil.).  Am- 
monium hydroxide  (sol.).  Carbon  tetrachloride  or  disulphide. 

a.  Place  not  over  0.2  c.c.  of  graphite  in  each  of  three  test- 
tubes.    Add  5  c.c.  dilute  hydrochloric  acid,  as  an  example  of 
an  acid,  to  one.    Add  5  c.c.  of  ammonium  hydroxide,  chosen 
as  a  base,  to  the  second.    Add  4  c.c.  of  carbon  tetrachloride, 
chosen  as  a  solvent,  to  the  third. 

Shake  the  last  vigorously  (away  from  all  flames).  Does  the 
graphite  dissolve?  Name  a  solvent  for  carbon  (?). 

b.  Boil  the  two  other  samples  with  the  acid  and  base,  re- 
spectively.   Is  there  any  evidence  of  continued  action,  when 
the  tube  is  taken  out  of  the  flame?    Conclusion  (?). 

What  are  the  uses  of  graphite? 

EXERCISE  58 
CARBON  DIOXIDE  BY  OXIDATION 

Object:  To  observe  the  production  of  carbon  dioxide  when  wood  burns 
and  oxides  of  metals  are  reduced  by  carbon. 

Apparatus:  250  c.c.  bottle.  Mortar.  Trip  scales.  Hard  glass 
test-tube  with  1-hole  stopper  and  L-tube. 

Materials:  Limewater.  Splints.  Cupric  oxide  (powdered).  Char- 
coal (powdered).  Stannic  oxide  (powdered).  Lead  monoxide. 

a.  Place  10  c.c.  of  limewater  in  a  250  c.c.  bottle.  Burn  a 
splinter  of  wood  in  the  bottle,  taking  care  not  to  drop  any  ashes 
into  the  liquid.  Close  the  bottle  with  the  hand  and  shake  (?). 
If  the  change  is  not  distinct,  repeat  the  burning,  using  the  same 
limewater,  and  shake  again.  What  elements  does  wood  con- 
tain? Make  the  equations  for  the  reactions  of  the  carbon 
dioxide  with  the  limewater. 

6.  Mix  intimately  in  the  mortar  5  g.  of  cupric  oxide  and 
0.5  g.  of  powdered  charcoal.  Place  this  on  a  strip  of  paper, 


78  CARBON  DIOXIDE  BY  OXIDATION 

folded  V-shape,  and  slip  the  hard-glass  test-tube  over  the  paper. 
Turn  the  tube  round,  so  as  to  leave  the  mixture  in  it,  and  with- 
draw the  paper.  Insert  the  stopper  and  L-tube.  Place  10  c.c 
of  limewater  in  a  test-tube.  Clamp  the  tube  containing  the 
mixture  in  a  horizontal  position,  at  such  a  height  that  it  can  be 
heated,  and  let  the  L-tube  project  to  the  bottom  of  the  lime- 
water.  If  the  tube  is  too  short  to  reach  the  bottom,  add  a 
straight  glass  tube  and  rubber  connection.  The  purpose  is  to 
compel  any  gas  which  may  be  given  off  to  bubble  through  the 
entire  depth  of  the  limewater. 

Heat  the  mixture,  beginning  at  the  end  farthest  from  the 
stopper,  at  first  gently  and  then  strongly  and  persistently. 
What  change  takes  place  in  the  limewater?  Finally,  take  the 
tube  out  of  the  limewater  and  then  remove  the  flame.  When 
the  tube  is  cold,  grind  the  contents  in  the  mortar  with  water, 
and  wash  away  the  lighter  particles.  Examine  the  residue  (?). 
Make  the  equation  for  the  action  (?).  What  important  indus- 
trial processes  depend  on  this  reaction?  What  was  oxidized 
and  what  reduced  in  this  reaction? 

c.  Perform  the  same  experiment,  using  5  g.  of  oxide  of  tin 
and  1  g.  of  charcoal.    Answer  the  same  questions  as  in  a. 

d.  Perform  the  same  experiment,  using  2  g.  of  litharge  (lead 
monoxide)  and  2  g.  charcoal.    In  this  instance  heat  gently. 
Answer  the  same  questions  as  in  a. 

EXERCISE  59 
CAKBON  DIOXIDE  —  PKEPAEATION  AND  PROPERTIES 

Object:   To  prepare  carbon  dioxide  and  to  observe  its  properties. 

Apparatus:  Gas  generating  bottle  (90  c.c.),  2-hole  stopper,  thistle 
tube,  L-tube  and  rubber  delivery  tube.  3  wide-mouth  bottles 
(250  c.c.)  and  glass  plates.  Test-tubes.  Taper. 

Materials:  Marble  (chips).  Hydrochloric  acid  (dil.).  Litmus 
(sol . ) .  Limewater. 

a.  Use  the  apparatus  in  Fig.  10,  Ex.  10  a.  Slide  into  the 
bottle  (do  not  drop  them  in)  enough  marble  chips  to  fill  it  to 
a  depth  of  one  inch,  and  connect.  Add  dilute  hydrochloric  acid 
and  fill  all  bottles  with  the  gas  by  upward  displacement  of  air. 
Cover  the  bottles  with  glass  plates. 

To  a  test-tube  (clean)  full  of  water  add  some  litmus  solution. 


CARBON  MONOXIDE  79 

Pour  half  of  the  mixture  into  another  test-tube  and  keep  the 
latter  for  reference.  Through  a  clean  glass  tube,  pass  carbon 
dioxide  into  the  other  half  (see  c). 

b.  Light  a  taper  and  pour  the  gas  from  one  of  the  bottles  over 
the  flame,  as  you  would  water  (?).     Does  the  gas  support  com- 
bustion?   Is  the  gas  heavier  or  lighter  than  air?    Give  the 
reason  for  your  answer  (?). 

To  learn  whether  the  gas  is  soluble  in  water,  pour  about 
10  c.c.  of  water  into  a  bottle  of  the  gas,  cover  quickly  and  firmly 
with  the  palm  of  the  hand,  and  shake  vigorously.  Is  the  hand 
held  against  the  mouth  of  the  bottle  by  atmospheric  pressure, 
or  not?  Is  the  gas  soluble? 

To  ascertain  whether  the  gas  diffuses  upwards,  set  the  emptied 
bottle  (now  filled  with  air)  over  the  full  one,  and  mouth  to  mouth 
with  it,  and  withdraw  the  plate.  After  ten  minutes  (meanwhile, 
do  c),  replace  the  glass  plate  between  the  bottles,  remove  the 
upper  bottle,  along  with  the  plate,  and  set  it  upright  upon  the 
table.  Slip  the  plate  aside  for  a  moment,  add  some  limewater, 
replace  the  plate,  and  shake  (?).  Did  the  greater  density  of  the 
carbon  dioxide  prevent  its  diffusing  into,  and  displacing  a  part  / 
of  the  air? 

c.  Examine  the  litmus  solutions,  and  compare  their  color  (?). 
What  property  has  the  solution  of  carbon  dioxide  in  water? 
How  is  the  substance  formed  (equation)? 

d.  Make  a  list  of  the  properties  observed:  Color  (?),  odor  (?), 
density  (?),  diffusibility  (?),  solubility  (?),  supports  combustion 
or  not  (?),  what  chemical  action  on  water  (?).     Note  which  of 
these  properties  are  physical  and  which  chemical  (?). 

e.  Why  will  any  other  acid  act  on  marble  as  does  hydrochloric 
acid  [333]? 

If  you  obtained  a  carbonate  as  an  unknown  substance,  how 
should  you  proceed  to  identify  it? 

EXERCISE  60 
CARBON  MONOXIDE 

Object:   To  prepare  carbon  monoxide  and  to  observe  its  properties. 

Apparatus:  Flask  (200  c.c.)  with  2-hole  stopper.  Funnel,  pinch- 
clamp,  straight  tube  and  rubber  connection.  L-tube  and  de^ 
livery  tube.  Trough.  3  wide-mouth  bottles  (250  c.c.),  3  glass 


80  HYDROCARBONS 

Materials:  Sulphuric  acid  (cone.).  Formic  acid.  Limewater. 
Taper. 

Caution:  The  gas  is  poisonous  (HOOD).  Do  not  allow  it  un- 
necessarily to  escape  into  the  room. 

a.  Fit  a  200  c.c.  flask  with  a  2-hole  stopper,  L-tube  and  rubber 
delivery  tube,  and  the  funnel  and  straight  tube  with  pinchclamp 
shown  in  Fig.  16  (Ex.  37).     Place  the  flask  on  the  ring  of  the  iron 
stand  (with  wire  gauze),  at  a  suitable  height  for  heating  by  a 
small  flame.    Hold  the  funnel  erect  in  the  clamp.    Extend  the 
delivery  tube,  if  necessary,  by  adding  a  bent  glass  tube  so  that 
the  gas  may  be  collected  over  water.    Remove  the  stopper,  pour 
into  the  flask  about  1  cm.  depth  of  concentrated  sulphuric  acid, 
and  replace  the  stopper.    Pour  some  formic  acid  into  the  funnel, 
and  never  allow  this  entirely  to  run  out  during  the  experiment. 

Warm  the  sulphuric  acid  gently  (small  flame),  and  then  admit 
the  formic  acid  a  drop  or  two  at  a  time.  Collect  three  bottles 
full  of  the  gas.  What  will  the  first  bottle  largely  contain?  Do 
not  use  this  one. 

b.  Light  a  taper,  raise  one  bottle  out  of  the  water  and  plunge 
the  taper  up  into  it.    Does  the  gas  burn?    Does  the  taper  burn 
in  the  gas? 

c.  Slide  the  glass  plate,  for  a  moment,  partly  off  a  second 
bottle  of  the  gas  and  pour  in  a  little  limewater.    Shake  (?). 
Now  light  a  taper,  set  fire  to  the  gas  in  this  bottle,  replace  the 
cover  instantly,  and  shake  again  (?).    What  product  is  formed 
when  carbon  monoxide  burns?     Make  the  equation  (?). 

d.  Summarize  the  properties  of  carbon  monoxide:   color  (?), 
solubility  in  water  (?),  burns  or  not  (?),  supports  combustion 
or  not  (?).    What  is  the  density  compared  with  that  of  air 
[340]? 

How  could  you  distinguish  burning  hydrogen  from  burning 
carbon  monoxide? 

EXERCISE  61 

HYDROCARBONS 

Object:  To  make  two  typical  hydrocarbons,  to  ascertain  their  proper- 
ties, and  to  compare  the  luminosities  of  their  flames. 

Apparatus:  Test-tube.  1-hole  stopper  and  L-tube.  250  c.c. 
bottle.  12"  rubber  tube.  Evaporating  dish.  Beaker. 


HYDROCARBONS  81 

Materials:  Soda    lime.    Sodium     acetate.     Limewater.  t  Litmus 
papers.     Hydrochloric  acid  (cone.).     Calcium  carbide. 

a.  Methane.    Mix  about  2  c.c.  each  of  powdered  soda  lime 
and  sodium  acetate  and  place  the  mixture  in  a  test-tube.     Clamp 
this  in  a  horizontal  position  and  insert  in  it  a  1-hole  stopper  with 
L-tube  pointed  upwards.    Tap  the  test-tube  to  cause  the  mix- 
ture to  settle  and  heat  it  gently  (small  flame).     Slip  a  test-tube 
over  the  vertical  part  of  the  L-tube.    When  the  gas  in  this  test- 
tube,  on  being  lighted   (after  removal  to  a  distance),  burns 
quietly,  set  fire  to  the  jet  issuing  from  the  apparatus. 

b.  Describe  the  structure  of  the  flame  (?).     How  luminous 
is  the  flame?    Hold  a  bottle  so  that  the  flame  burns  inside  it. 
If  a  dew  appears  in  the  bottle,  what  is  it?    Inference  (?).    With- 
draw and  close  the  bottle,  and  shake  the  contents  with  some 
limewater  (?).    Inference  (?). 

Extinguish  the  flame,  and  test  the  gas  for  acid  or  basic  proper- 
ties by  holding  in  it  moistened  strips  of  red  and  blue  litmus 
paper  (?). 

c.  Summarize  the  observed  physical  and  chemical  properties 
of  the  gas  (?). 

d.  Place  some  limewater  in  a  test-tube.    When  the  appara- 
tus used  in  b  has  become  cold,  attach  a  rubber  tube,  add  5  c.c. 
of  concentrated  hydrochloric  acid,  replace  the  stopper,  and  let 
the  issuing  gas  bubble  through  the  limewater  (?).     Inference 
(?) .    What,  besides  methane,  is  the  other  product  of  the  reaction? 
Write  the  equations  for  the  original  action  (?)  and  for  the  action 
of  the  acid  on  the  product  (?). 

e.  Acetylene.    Fill  a  test-tube  with  water.    Invert  it  in  an 
evaporating  dish  partly  filled  with  water.     Place  a  small  piece 
of  calcium  carbide  in  the  water,  and  collect  the  gas  in  the  test- 
tube. 

Set  fire  to  the  gas  in  the  test-tube.  Compare  the  luminosity 
of  the  flame  with  that  of  methane  (?).  Close  the  tube,  add  a 
little  limewater  and  shake  (?).  Inference  (?). 

/.  Summarize  the  observed  physical  and  chemical  proper- 
ties of  the  gas  (?).  Compare  its  density  with  that  of  air  (?). 

g.  Pour  the  liquid  in  the  evaporating  dish  into  a  beaker  (?). 
Test  it  with  litmus  papers  (?).  What  is  the  suspended  solid? 
Write  the  equation  for  the  interaction  of  the  carbide  and  water 


82  FLAME 

EXERCISE  62 
FLAME 

Object:  To  learn  the  source  of  the  luminosity,  and  the  structure  of  a 
flame.  To  find  out  the  use  of  the  holes  at  the  base  of  a  Bunsen 
burner.  To  observe  the  nature  of  the  flame  of  a  taper. 

Apparatus:   Evaporating  dish. 

Materials:   Splints.     Calcium  carbonate  (powdered). 

a.  Unscrew  the  tube  of  the  Bunsen  burner,  turn  on  the  gas, 
and  light  it  (?).     Turn  off  the  gas  and  replace  the  tube.     Make 
a  drawing  of  the  vertical  section  of  the  burner  through  the  feed 
pipe  (?). 

Light  the  gas  again  and  hold  one  side  of  the  evaporating 
dish,  first  in  the  non-luminous  flame  and  then  in  the  luminous 
one  (?).  Which  substance  causes  the  light  (?)  and  how?  Why 
does  this  substance  remain  for  a  time  suspended  in  the  flame, 
instead  of  burning  at  once? 

b.  Hold  a  splint  across  the  luminous  flame  close  to  the  bot- 
tom, and  examine  the  wood  (?).    Inference  (?).    Repeat  with 
the  non-luminous  flame  (?).    Why  is  the  interior  of  the  flame 
cold? 

c.  Is  any  gas  entering  or  escaping  from  the  holes  at  the  base? 
To  answer  this,  light  a  splint,  blow  the  flame  out,  and  hold  the 
smoking  end  close  to  the  holes  (?) .     Confirm  by  scattering  a  very 
small  amount  of  pulverized  calcium  carbonate  on  a  piece  of  paper, 
and  shaking  it  off  so  that  it  falls  past  one  hole.    Observe  the 
flame  (?). 

Hold  the  burner  up  and  blow  a  sudden  puff  of  air  towards 
one  of  the  holes  (?).  What  is  the  effect  of  increasing  the  supply 
of  air? 

d.  Light  a  taper  and  a  splint.    Blow  out  the  flame  of  the 
taper  and  instantly  apply  the  flame  of  the  splint  to  the  ascending 
"smoke"   (?).     Repeat,  noting  whether  the  taper  can  be  re- 
lighted at  a  distance  from  the  wick  (?).    Explain.    Is  the  flame 
of  a  taper  a  gas  flame  or  not? 


BORAX  BEAD  TESTS  83 

EXERCISE  63 
BORAX  BEAD  TESTS 

Object :  To  learn  the  use  of  a  borax  bead  for  recognizing  the  metallic 
elements  in  an  unknown  compound. 

Apparatus :  Watch-glass.     Platinum  wire. 

Materials:  Borax  (powdered).  Cobalt  chloride.  Manganese  di- 
oxide. Potassium  dichromate.  Ferric  chloride.  Nickel  sul- 
phate. Cupric  sulphate.  Unknowns. 

a.  Place  some  powdered  borax  on  a  watch-glass.     Heat  the 
platinum  wire  and  dip  the  glowing  end  in  the  borax.     Use  the 
straight  wire,  without  any  loop.     Now  hold  the  wire  in  the  flame 
and  observe  the  behavior  of  the  borax  (?).    What  vapor  causes 
it  to  puff  up  [363]?    The  bead  must  be  small,  to  avoid  its  drop- 
ping off. 

Lower  the  flame  until  it  is  so  small  that  it  can  be  sheltered 
from  drafts  by  the  hands.  Close  the  air-holes  until  a  small 
luminous  tip  appears  in  the  interior  of  the  flame.  This  is  the 
reducing  portion  of  the  flame  (Why?).  The  blue  tip  and  whole 
exterior  of  the  flame  is  the  oxidizing  part  (Why?). 

b.  Heat  the  borax  bead  and  touch  with  it  a  small  particle  of 
a  compound  of  cobalt.     Hold  the  glass  rod  between  the  first  and 
second  fingers  of  the  right  hand,  so  that  when  the  hands  surround 
the  flame,  the  bead  is  held  in  the  latter.    Hold  the  bead  in  the 
oxidizing  flame. 

Examine  the  bead  when  cold  (?).  If  it  is  not  distinctly 
colored,  pick  up  another  particle  of  the  cobalt  compound  and 
heat  again.  If  the  bead  is  opaque,  too  much  of  the  compound 
has  been  taken.  Remove  the  bead  and  start  again. 

To  remove  the  bead,  heat  it  red  hot  and,  holding  it  over  the 
sink  or  waste-jar,  tap  the  wire  with  a  pencil. 

Now  hold  the  bead  in  the  reducing  flame,  persistently,  keep- 
ing the  flame  steady  by  sheltering  it  with  the  hands  (?). 

Finally,  remove  the  bead  and  make  another.  If  this  shows 
the  cobalt  color,  remove  it  and  repeat  until  a  colorless  bead  is 
obtained. 

c.  Repeat  b,  touching  a  particle  of  manganese  dioxide  with 
the  heated  bead,  and  examine  in  the  oxidizing  (?)  and  reducing 
flames  (?).    Tabulate  the  results  of  6,  c,  d,  e  and  /  as  shown  on 
page  84 


84  SODIUM  BICARBONATE.    ACID  SALTS 

d.  Repeat  c  with  a  compound  of  chromium  (?). 

e.  Repeat  c  with  a  compound  of  iron  (?). 

/.  Repeat  with  compounds  of  nickel  (?)  and  copper  (?). 

COLOR  OF  BEAD 

COMPOUND  USED  FORMULA  OXIDIZING  REDUCING 

FLAME  FLAME 

g.  Obtain  an  unknown  substance  and  identify  the  metallic 
element  in  it. 

• 

EXERCISE  64 
SODIUM  BICARBONATE.    ACID  SALTS 

Object:  To  prepare  sodium  bicarbonate  by  the  Solvay  process.    To 

study  the  effect  of  heat  on  the  bicarbonate  and  on  another  acid 

salt. 
Apparatus:    Graduated    cylinder.     Test-tube    (large)    and   cork. 

Trip  scales.     Gas  generating  bottle  with  thistle,  L-,  rubber,  and 

glass  delivery  tubes.     Test-tube,   1-hole  stopper  and  L-tube. 

Test-tubes. 
Materials:  Ammonium  hydroxide  (sol.).    Ammonium  carbonate. 

Sodium  chloride.     Marble  (chips).     Hydrochloric  acid.     Filter 

paper.     Limewater.    Sodium  bisulphite. 

a.  Preparation.    Measure  24  c.c.  of  ammonium  hydroxide 
solution  and  12  c.c.  of  water  into  a  large  test-tube,  add  8  g.  of 
powdered  ammonium  carbonate,  cork  the  tube  and  shake  until 
the  salt  is  dissolved.    Add  solid,  powdered  sodium  chloride  in 
excess  and  shake  vigorously  until  the  liquid  is  saturated. 

Decant  the  clear  liquid  into  another  test-tube,  and  lead  into 
it  carbon  dioxide  (made  as  in  Ex.  59  a)  until  a  copious  precipi- 
tate of  sodium  bicarbonate  has  appeared.  While  this  is  going 
on,  proceed  with  b. 

Filter,  and  dry  the  precipitate  by  pressing  between  filter 
papers.  Note  the  appearance  (?)  and  taste  (?). 

b.  Effect  of  Heating  the  Bicarbonate.    Place  some  sodium 
bicarbonate  in  a  test-tube  so  that  the  mouth  is  inclined  slightly 
downwards,  with  the  L-tube  dipping  into  limewater.    Warm 
the  bicarbonate  gently  with  a  small  flame.    What  gas  is  given 
off?    What  is  deposited  in  the  cool  part  of  the  tube?    Taste 
the  residue  when  cold  (?).    To  a  part,  add  an  acid  (?).    What 


HYDROLYSIS  85 

is  the  residue?    Write  the  equation  for  the  action  of  heat  on 
the  bicarbonate  (?). 

c.  Effect  of  Heating  Another  Acid  Salt.     Many  acid  salts 
[260]  behave,  when  heated,  as  sodium  bicarbonate  did  in  b, 
and  can  be  recognized  by  this  behavior.     Heat  a  little  sodium 
bisulphite  in  a  test-tube,  clamped  horizontally  (?).    What  gas 
(odor  ?)  is  given  off?     Is  water  liberated?    Write   the  .equa- 
tion (?). 

d.  Summarize  the  properties  of  sodium  bicarbonate  and  of 
sodium  carbonate,  namely,  color-  (?),  taste  (?),  effect  of  heat- 
ing  (?). 

EXERCISE  65 

HYDROLYSIS 

Object:  To  examine  several  salts  in  order  to  find  out,  by  the  reaction 

oj  the  solution,  which  interact  with  water  and  which  do  not,  and 

to  explain  the  result  in  each  case. 
Apparatus :    Test-tubes. 
Materials:    Litmus  papers.      Sodium    carbonate    (sol.).     Cupric 

sulphate  (sol.).     Potassium  iodide  (sol.).    Aluminium  sulphate. 

Lead  nitrate  (sol.).    Sodium  nitrate. 

a.  Test  some  sodium  carbonate  solution  with  litmus  papers 
(?).    Explain  [368]  the  reaction  of  the  solution  (?). 

b.  Repeat  a  with  cupric  sulphate  solution  (?)  and  explain  (?) . 

c.  Repeat  a  with  solutions  of  potassium  iodide,  aluminium 
sulphate,  lead  nitrate,  and  sodium  nitrate  (?).    Write  the  equa- 
tion for  hydrolysis  in  each  case  (?).    Where  there  is  a  reaction 
towards  litmus,  explain  it  (?).     If  there  is  none,  explain  why  (?). 

d.  Dissolve  a  single  crystal  of  sodium  sulphide  in  water,  and 
test  the  solution  with  litmus  paper  (?).    WTiat  ionic  substance 
causes  this  reaction?    Which  of  the  two  substances  taken  is 
capable  of  furnishing  this  ion?    Formulate  the  interaction  of 
the  two  original  substances  and  explain  it. 

EXERCISE  66 
POTASSIUM  NITRATE  —  PREPARATION 

Object:   To  prepare  potassium  nitrate,  and  to  study  the  influence  of 
solubility  on  the  products  obtained  in  double  decomposition. 


86  POTASSIUM  NITRATE 

Apparatus:  Test-tubes.      Trip    scales.      2   beakers.      Graduated 

cylinder.     Glass  rod.     Watch-glass.     Lens. 
Materials:  Potassium  chloride.     Sodium  nitrate. 

a.  Dissolve  22  g.  of  potassium  chloride  in  45  c.c.  of  boiling 
water  in  a  test-tube. 

Boil  20  c.c.  of  water  in  a  beaker  (set  on  the  wire  gauze)  and 
add  25  g.  of  sodium  nitrate.  When  this  has  dissolved,  add  the 
boiling  solution  of  potassium  chloride  and  continue  heating  for 
a  minute  or  so  (?). 

Allow  the  mixture  to  settle  and  immediately  pour  the  hot 
liquid  off  the  crystalline  residue  into  another  clean  beaker. 
Examine  the  two  products  in  6  and  c  respectively. 

6.  Pour  a  few  c.c.  of  hot  water  on  to  the  crystalline  residue, 
stir  with  a  rod  to  wash  the  residue  and  drain  away  the  liquid. 

Taste  the  residue  (?).  Dissolve  a  part  in  a  very  little  hot 
water,  pour  several  drops  on  a  watch-glass  and  examine  the 
crystals,  when  they  appear,  with  a  lens  (?).  Draw  a  couple  of 
them  (?).  What  is  the  substance? 

c.  When  it  is  cold,  examine  the  liquid  that  was  poured  off  into 
the  beaker  in  a  (?).    What  form  do  most  of  the  crystals  show? 
Are  there  any  cubical  crystals  (lens)?    Pour  away  the  liquid. 
Dissolve  the  crystals  in  a  very  little  boiling  water  and  set  aside. 
This  is  called  recrystallization.    Examine  the  final  crystals  and 
draw  two  of  them  (?). 

d.  Write  the  equation  for  the  action  (?).    Examine  the  fol- 
lowing solubilities  (grams,  dissolving  in  100  c.c.  of  water  at  the 
temperatures  given) : 

10°      100°  10°     100° 

Potassium  chloride    32        57      Potassium  nitrate      13      246 
Sodium  nitrate          80      182      Sodium  chloride         36        39 

The  action,  being  a  double  decomposition,  is  reversible  and 
therefore  incomplete.  All  four  substances  were  present  in  the 
mixture  when  the  latter  was  first  made.  Which  is  the  least 
soluble  of  the  four  salts  at  100°?  Why  was  the  sodium  chloride 
the  substance  precipitated  in  the  hot  mixture?  Why  did  potas- 
sium nitrate  remain  dissolved?  Why  did  it  come  out  so  copi- 
ously when  the  liquid  cooled?  Why  were  there  few  crystals  of 
sodium  chloride  mixed  with  it? 


RECOGNITION  OF  SUBSTANCES  I  87 

EXERCISE  67 
RECOGNITION  OF  SUBSTANCES  I 
(Mainly  certain  negative  radicals) 

Object:  To  learn  how  substances  may  be  recognized  by  their  proper- 
ties, and  to  review  the  methods  of  preparation  and  properties 
studied  in  previous  exercises. 

Apparatus:  Test-tubes.    Glass  rod.    Watch  glass. 

Materials:  Unknowns.  Litmus  papers.  Filter  paper.  Sodium 
hydroxide  (sol.).  Limewater.  Sulphuric  acid  (cone.).  Barium 
chloride  (sol.).  Hydrochloric  acid  (cone.). 

a.  Obtain  [Instructor]  a  single  unknown  solid  substance. 
This  will  contain  one  of  the  following  radicals: 

ammonium  (NH4)  sulphite  (S03) 

chloride  (Cl)  sulphate  (S04) 

carbonate  (C03)  formate  (C02H) 

sulphide  (S)  base  (OH) 

In  the  case  of  a  salt  (except  one  of  ammonium)  we  shall  limit 
ourselves  to  identifying  the  negative  radical  only.  The  other 
positive  radicals  will,  in  any  case,  be  limited  to  (Na),  (K), 
and  (Ca). 

Record  at  the  time  the  result  of  each  observation.  Record 
negative  results  also. 

6.  External  Examination  [376].  Begin  by  recording  the  state 
(?),  crystalline  form  (?),  color  (?),  and  odor  (?). 

c.  Solubility  and  Reaction  of  Solution.    Use  a  few  particles 
to  find  out  whether  it  is  soluble  in  water  (?).     If  in  doubt, 
proceed  as  in  Ex.  10  /.    Apply  a  drop  of  the  solution  to  litmus 
papers  (?). 

d.  Effect  of  Heating  [377].    Heat  0.5  c.c.  in  a  dry  test-tube. 
Watch  the  substance.     Does  it  melt  (?),  char  (?),  or  otherwise 
change  (?)?    Note  also  gases  or  vapors. 

If  WATER  VAPOR  is  given  off  and  condenses  (?),  the  substance 
may  be  a  hydrate,  an  organic  substance,  or  calcium  hydroxide. 
Incline  the  tube  downwards,  drive  all  the  water  off,  dry  out  the 
tube  with  filter  paper,  and  continue  heating. 

Does  it  now  char  (?),  change  (?),  or  give  gases  or  vapors? 


88  RECOGNITION  OF  SUBSTANCES  II 

If  a  SUBLIMATE  (solid  deposit  in  the  tube)  appears  (?),  it  is 
a  salt  of  ammonium.  Note  the  odor  (?)  and  apply  the  test 
(Ex.51/). 

A  COLORLESS  GAS  with  an  ODOR  (?)  may  be  ammonia,  sulphur 
dioxide,  or  hydrogen  sulphide,  or  gases  from  the  charring  of 
carbohydrates  (see  e). 

A  COLORLESS  GAS  with  NO  ODOR.  Examine  for  carbon  dioxide 
by  inserting  a  rod  dipped  in  limewater  (?).  If  you  get  a  positive 
result,  what  was  the  unknown  substance  [336]? 

e.  Effect  of  Sulphuric  Acid  [379].  To  0.5  c.c.  of  the  sub- 
stance add  two  or  three  drops  (not  more)  of  concentrated  sul- 
phuric acid  (?).  If  necessary,  warm  gently  (?).  Watch  the 
substance,  and  look  out  for  gases. 

A  COLORLESS  GAS  (bubbling),  which  FUMES  in  the  breath,  is 
hydrogen  chloride.  If  it  does  fume,  what  was  the  substance 
[126]? 

A  COLORLESS  GAS  which  does  NOT  FUME  may  have  an  ODOR 
(?).  If  the  odor  is  that  of  hydrogen  sulphide,  what  do  you  infer 
[253]?  If  it  is  that  of  sulphur  dioxide,  inference  [258,  par.  4]  (?). 

A  COLORLESS  GAS,  which  does  NOT  FUME  and  is  ODORLESS,  may 
be  carbon  dioxide.  Test  with  rod  dipped  in  limewater  (?). 
Inference  (?).  It  may  be  carbon  monoxide.  Try  whether  it  is 
combustible  (?).  Inference  [340]  (?). 

If  there  is  NO  BUBBLING,  there  is  no  gas.  The  substance  may 
be  a  sulphate.  Test  (Ex.  47,  d)  (?).  It  may  be  a  base  (test?). 

/.  Report.  State  your  conclusion,  with  the  reasons  there- 
for (?). 

g.  Obtain  a  second  unknown  and  proceed  as  before  (?). 

EXERCISE  68 

RECOGNITION  OF  SUBSTANCES  II 
(Negative  Radicals) 

Object:  Same  as  in  Ex.  67,  which  see. 

Apparatus:  Test-tubes.     Glass  rod.    Watch-glass. 

Materials:  Unknowns.  Litmus  papers.  Filter  paper.  Sodium 
hydroxide.  Limewater.  Splints.  Ferrous  sulphate  (sol.). 
Sulphuric  acid  (cone.).  Potassium  dichromate  (sol.).  Sul- 
phuric acid  (dil.).  Ammonium  molybdate  (sol.). 


RECOGNITION  OF  SUBSTANCES  II  89 

a.  Obtain   [Instructor]   a  single   unknown  solid   substance. 
This  will  contain  one  of  the  following  radicals : 

peroxide  (02)  phosphate  (P04) 

nitrate  (N03)  bicarbonate  (HC03) 

chloride  (Cl)  carbonate  (C03) 

bromide  (Br)  bisulphite  (HS03) 

iodide  (I)  sulphite  (SO,) 

The  positive  radical  may  be  (NH4),  (K),  (Na),  or  (Ca). 
Limit  yourself  to  identifying  the  negative  radical  and  (NH4). 
Record  immediately  the  result  of  each  observation.     Record 
negative  results  also. 

b.  External  Examination  [376].       Record  the  state  (?),  crys- 
talline form  (?),  color  (?),  and  odor  (?). 

c.  Solubility  and  Reaction  of  the  Solution.    With  a  few 
particles,  try  the  solubility  in  water  and,  if  in  doubt  use  the 
method  in  Ex.  10  /  (?).     Test  the  solution  on  litmus  papers  (?). 

d.  Effect  of  Heating  [377].    Heat  0.5  c.c.    Does  the  sub- 
stance melt  (?),  char,  or  otherwise  change  (?).    Note  also  gases 
or  vapors  (?). 

If  WATER  VAPOR  is  given  off  (?),  the  substance  may  be  a 
hydrate  or  an  acid  salt.  To  prevent  cracking  of  the  tube,  re- 
move the  water  with  filter  paper. 

A  SUBLIMATE  indicates  a  salt  of  NH4  (test,  Ex.  51  /). 

A  COLORLESS  GAS  with  an  ODOR  (?)  may  be  ammonia  or  sul- 
phur dioxide  (Ex.  64  c).  Inference? 

A  COLORLESS  GAS  with  NO  ODOR  (?).  Examine  for  carbon 
dioxide  (lime-water  test)  oxygen  from  a  peroxide  or  nitrate 
(test),  or  nitrous  oxide  [315]  (test,  Ex.  54  c).  Inference? 

e.  Effect  of  Sulphuric  Acid  [379].   To  0.5  c.c.  add  2  or  3  drops 
(not  more)  of  concentrated  sulphuric  acid  (?).     If  necessary, 
warm  gently  (?). 

A  GAS  (bubbling)  with  FUMES  in  the  breath.  If  accompanied 
by  a  COLORED  VAPOR,  it  may  be  hydrogen  bromide  with  free 
bromine,  or  hydrogen  iodide  with  free  iodine.  Nitric  acid  vapor, 
also,  may  be  faintly  colored  with  N02  [309].  Inference? 

A  GAS  which  FUMES,  but  is  NOT  COLORED,  may  be  hydrogen 
chloride,  or  nitric  acid  (test,  Ex.  52  d).  Inference? 

A  GAS  (bubbling)  may  NOT  FUME  and  may  NOT  BE  COLORED. 
If  it  has  an  ODOR,  it  may  be  sulphur  dioxide  from  a  sulphite  or 
bisulphite.  The  latter  would  give  sulphur  dioxide  under  d  also, 
the  former  would  not.  Inference? 


90  CALCIUM  OXIDE  AND  HYDROXIDE 

A  GAS,  not  FUMING,  NOT  COLORED,  and  ODORLESS  may  be 
oxygen  from  some  oxides  or  a  peroxide  (test,  Ex.  40  d),  or  car- 
bon dioxide  (test)  from  a  carbonate  or  bicarbonate.  The  last 
would  give  carbon  dioxide  under  d  also,  a  soluble  carbonate  of 
K  or  Na  would  not,  but  calcium  carbonate  or  ammonium  car- 
bonate would  do  so.  Inference? 

If  there  is  NO  GAS  (no  bubbling),  the  substance  may  be  a 
phosphate  (test,  Ex.  55  6).  Inference? 

/.  Test  the  unknown  for  the  (NH4)  radical  (Ex.  51  /). 

g.  Report.  State  your  conclusion,  with  the  reasons  therefor  (?). 

h.  Obtain  a  second  unknown  and  proceed  as  before  (?). 

EXERCISE  69 
CALCIUM  OXIDE  AND  HYDROXIDE 

Object:  To  observe  the  formation  of  calcium  oxide,  and  the  actions  of 
water  and  of  an  acid  upon  it. 

Apparatus :  Wire  gauze.  2  watch  glasses.  Glass  rod.  Evaporat- 
ing dish.  Test-tubes. 

Materials:  Marble  (chips).  Litmus  paper  (red).  Quicklime 
(fresh).  Hydrochloric  acid  (dil.) 

a.  Select  two  small  chips  of  marble.    Place  one  on  the  wire 
gauze  and  heat  with  the  full  flame  for  10  minutes  (meanwhile 
proceed  with  c  and  d).    Examine  it  and  compare  its  appearance 
with  that  of  the  unheated  fragment  (?).    Write  the  equation 
for  the  change  (?). 

b.  Place  two  strips  of  red  litmus  paper  in  two  watch  glasses. 
Lay  one  of  the  fragments  from  a  on  each,  and  moisten  with  water 
carried  on  a  glass  rod  (?)      What  has  been  formed  by  the  action 
of  the  water?    Write  the  equation  (?).    What  sort  of  oxide  is 
calcium  oxide  [386]? 

c.  Place  a  lump  of  quicklime  in  the  evaporating  dish,  add  a 
little  water  (only  enough  to  wet  the  lower  quarter  of  the  lump) 
and  warm  gently  (?).    Write  the  equation  (?). 

d.  Place  about  1  c.c.  of  powdered  fresh  quicklime  in  a  test- 
tube,  add  dilute  hydrochloric  acid,  shake,  and  warm  if  necessary 
(?).    Write  the  equation  (?). 

For  comparison,  take  a  chip  of  marble  and  cover  it  with  dilute 
hydrochloric  acid  (?).  Write  the  equation  (?).  What  is  the 
reason  for  the  difference? 


MhA^ 


ir 


HARD  WATER  91 

e.  Summarize  the  properties  of  marble  and  quicklime:  color 
(?),  appearance  (?),  effect  of  heating  (?),  action  of  water  (?), 
action  of  an  acid  (?). 

EXERCISE  70 
HARD  WATER 

Object:  To  learn  the  means  of  detecting  hardness  in  water,  and  two 

ways  of  removing  temporary  hardness. 
Apparatus:   Test-tubes.     Gas  generating  apparatus.     Graduated 

cylinder. 
Materials:  Soap  solution  (12  g.  per  1.).    Limewater.    Magnesium 

chloride  (sol.). 

a.  Soft  Water.       To  about  10  c.c.  of  distilled  water  add  soap 
solution  drop   by  drop,   shaking  between  drops.     Count  the 
number  of  drops  required  before  a  "permanent"  lather  or  froth 
is  obtained  (?).    A  "permanent"  froth  is  defined  as  one  which 
persists  for  three  minutes. 

Give  the  name  and  formula  of  one  typical  component  of  soap 
[389]? 

b.  Temporary  Hardness.    Take  5  c.c.  of  saturated  limewater 
(1.7  g.  Ca(OH)2  per  liter)  and  add  an  equal  volume  of  distilled 
water.    Pass  carbon  dioxide  (made  as  in  Ex.  59  a)  through  the 
half-saturated  limewater  steadily  until  two  changes  (?)   have 
occurred  (meanwhile  proceed  with  c).    Write  two  equations,  one 
for  each  change  [388]  (?).     The  clear  product  is  water  of  tem- 
porary hardness.    What  substance  is  present? 

c.  Calculation  of  the  Degree  of  Hardness.    What  weight 
(grams)  per  liter  of  calcium  hydroxide  was  contained  in  the 
diluted  limewater?    What  weight  (grams)  per  liter  of  CaCOs 
would  this  give  in  the  final  product  (?) 

d.  Action  of  Hardness  on  Soap.   To  2  c.c.  (measured)  of  the 
product  from  b  add  soap  solution  (noting  how  much)  and  shake 
until  a  "permanent"  lather  is  obtained  (?).    The  precipitate  is 
a  calcium  soap.    Write  the  formula  of  a  typical  component  of 
this  soap  (?).    Write  the  equation  and  name  each  substance  (?). 

e.  Removing  Temporary  Hardness  (softening).    To  2  c.c. 
(measured)  of  the  product  from  6,  add  1  c.c.  (measured)  of 
saturated  limewater  and  shake  (?).    What  is  the  precipitate 
[389]?    Now  add  soap  solution,  noting  how  much  is  required 


92  FLAME  TESTS 

to  form  a  "permanent"  lather  (?).  Was  the  amount  required 
as  great  as  in  d,  or  was  it  nearer  the  amount  used  in  a? 

/.  Boil  2  c.c.  (measured)  of  the  product  from  6  (?).  What  is 
the  precipitate?  When  the  liquid  is  cold,  add  soap  solutions  as 
in  e,  to  determine  whether  the  hardness  has  changed  (?). 

g.  Permanent  Hardness.  Dissolve  a  crystal  of  magnesium 
chloride  in  10  cc.  of  water,  add  soap  solution  and  shake  (?). 
Write  the  equation  (?)  and  name  each  substance  (?). 

h.  Test  the  city  water  with  soap  solution  (?). 


EXERCISE  71 

FLAME  TESTS 
(Positive  Radicals) 

Object:   To  observe  the  characteristic  colors  given  to  the  Bunsen  flame 

by  the  heated  vapors  of  compounds  of  six  metals,  and  to  use  them 

for  recognizing  six  positive  radicals. 
Apparatus:   Test-tube.     Iron   wire   (No.   20),   or  platinum  wire. 

Cobalt  glass.     (Optional:  Spectroscope.) 
Materials:  Chlorides    of    lithium,    calcium,    strontium,    barium, 

sodium,  and  potassium.     Hydrochloric  acid  (cone.). 

a.  On  six  pieces  of  paper  write  the  names  of  the  six  substances 
listed  above  and  obtain  on  each  a  few  particles  of  the  proper 
substance.     Provide  5  c.c.  of  concentrated  hydrochloric  acid  in 
a  test-tube. 

Hold  the  iron  (or  platinum)  wire  in  the  Bunsen  flame.  If  the 
flame  is  colored  by  it,  dip  the  wire  in  the  acid,  and  hold  it  in  the 
flame  until  the  latter  is  as  blue  as  usual.  Clean  the  wire  in  this 
way  (i.e.,  by  vaporizing  impurities)  before  and  after  each  of  the 
following  tests. 

b.  Heat  the  tip  of  the  cleaned  wire  and  quickly  touch  the 
first  named  of  the  substances.     Hold  the  wire  with  adhering 
particles  in  the  lower  part  of  the  outer  blue  layer  of  the  flame 
and  note  the  color  of  the  latter  (?). 

Repeat  with  the  next  three  substances,  and  tabulate  the  re- 
sults, giving  the  name  of  the  substance  (?),  its  formula  (?),  and 
the  color  (?). 

c.  Using  sodium  and  potassium  chlorides,  view  both  flames 
through  a  piece  of  cobalt  glass.     Which  tint  of  light  is  absorbed 


STARCH  AND  SUGARS  93 

by  the  glass,  and  does  not  reach  the  eye  (?),  and  which  tint 
passes  through  and  is  visible? 

Mix  the  two  chlorides  intimately,  and  observe  the  flame  with 
the  eye  (?).  Which  color  is  visible?  Why  is  the  other  invisible? 
Now  view  the  flame  of  the  mixture  through  cobalt  glass  (?). 
Which  metal  can  you  recognize  thus? 

d.  (Optional)    If  a  spectroscope  is  available,  the  spectra,  and 
particularly  that  of  sodium,  should  be  examined. 

e.  Obtain  [Instructor]  an  unknown  and  identify  it. 


EXERCISE  72 
STAECH  AND  SUGARS 

Object:  To  study  the  properties  of  starch  and  its  hydrolysis  into  glu- 
cose; and  to  learn  the  properties  of  two  sugars,  glucose  and  sucrose 
(ordinary  sugar). 

Apparatus:  Test-tubes.  Flask.  Funnel.  Beaker.  Glass  rod. 
Graduated  cylinder. 

Materials:  Fehling's  solution  No.  1  and  No.  2.*  Starch.  Hydro- 
chloric acid  (cone.).  Potassium  iodide  (sol.).  Iodine.  Sodium 
carbonate  (sol.).  Litmus  papers.  Sugar.  Molasses. 

a.  Starch  and  Glucose.    Shake  about  0.5  c.c.  of  starch  with 
20  c.c.  of  water  and  then  boil  (?).    Add  a  few  drops  of  the  liquid 
to  5  c.c.  of  Fehling's  solution  and  warm  the  latter  (?).     Does 
starch  change  Fehling's  solution? 

Place  three-fourths  of  the  remaining  starch  suspension  in 
a  flask,  set  it  on  the  wire  gauze,  add  5  or  6  drops  of  concentrated 
hydrochloric  acid,  and  boil  gently  for  ten  minutes.  Place  the 
funnel  in  the  mouth  of  the  flask,  to  diminish  the  loss  by  evapora- 
tion, and  add  a  little  water  when  necessary  so  as  to  keep  the 
volume  constant. 

b.  While  this  is  going  on,  cool  the  rest  of  the  starch  sus- 
pension in  running  water  and  pour  it  into  a  beaker  full  of  cold 
water.    Add  one  drop  from  5  c.c.  of  a  solution  of  potassium 
iodide  in  which  a  single  crystal  of  iodine  has  been  dissolved  (?). 

e.  Cool  the  contents  of  the  flask  (from  a)  and  add  sodium 

*  No.  1:  69.3  g.  of  CuSO4,5H2O  with  water  to  make  1  liter.  No.  2: 
350  g.  Rochelle  salt  and  100  g.  sodium  hydroxide  with  water  to  make 
1  liter.  Mix  equal  volumes  (measured)  just  before  use. 


94  AGRICULTURE 

carbonate  solution  drop  by  drop,  shaking  between  drops,  and 
touching  the  edge  of  a  piece  of  litmus  paper  with  a  glass  rod 
dipped  in  the  liquid,  until  the  liquid  gives  faint  alkaline  reaction. 
Now  add  a  few  drops  of  this  liquid  to  5  c.c.  (measured)  of  Feh- 
ling's  solution  and  warm  the  latter  [401]  (?).  Add  more  of  the 
liquid,  boil  again,  and  continue  until  the  blue  color  is  gone.  It 
takes  0.005  g.  of  glucose  to  reduce  and  decolorize  1  c.c.  of  Feh- 
ling's  solution.  What  amount  of  glucose  was  contained  in  the 
part  of  the  liquid  you  added? 

d.  Sucrose.    Dissolve  about  0.5  g.  of  sucrose  (ordinary  sugar) 
in  20  c.c.  of  water  and  repeat  a  and  c  with  this  liquid.     Does 
sucrose  reduce  Fehling's  solution?     Do  acids  hydrolyze  it  to 
give  glucose?    Write  the  equation.     The  hydrogen-ion  of  the 
acid  acts  as  a  contact  agent.    Why  is  it  not  included  in  the 
equation? 

e.  Dissolve  about  0.5  c.c.  of  molasses  in  water  and  test  for 
glucose  as  in  a,  par.  1  (?). 

/.  Tabulate  the  physical  and  chemical  properties  of  starch, 
glucose,  and  sucrose  separately  as  follows:  color  (?),  solubility 
(?),  action  on  Fehling's  solution  (?),  action  of  dilute  acids  (?) 


EXERCISE  73 
AGRICULTURE.    ACID  AND  ALKALINE  SOILS 

Object:  To  ascertain  whether  a  soil  is  acid  or  alkaline,  and  to  measure 
the  acidity  of  an  acid  soil. 

Apparatus:  Watch-glass.  Wide-mouth  bottle.  Graduated  cylin- 
der. Burette.  Beaker.  Glass  rod. 

Materials:  Soil.  Potassium  nitrate  (sol.).  Sodium  hydroxide 
(sol.).  Phenolphthalein  (sol.). 

a.  Litmus  Test.  Place  a  red  and  a  blue  piece  of  litmus  paper 
on  a  large  watch-glass.     Make  the  soil  to  be  tested  into  a  paste 
with  distilled  water,  and  press  it  on  to  the  litmus  papers.     Place 
another  watch-glass,  to  hold  the  soil  against  the  paper  for  15 
minutes.     Note  whether  the  soil  gives  an  acid  or  an  alkaline  test. 

b.  Measurement  of  Acidity  in  Soil.    Place  100  g.  of  an  acid 
soil  in  a  400  c.c.  (or  12  oz.)  wide-mouthed  bottle.    Add  250  c.c. 
of  normal  potassium  nitrate,  stopper  the  bottle,  and  shake  the 
bottle  at  intervals  of  five  minutes  by  hand.    Let  the  mixture 


FERTILIZERS  95 

stand  overnight.  Withdraw  125  c.c.  of  the  clear  liquid  from  the 
top,  boil  it  for  ten  minutes  to  expel  carbon  dioxide,  cool  it,  and 
titrate  with  normal  sodium  hydroxide,  using  phenolphthalein 
as  indicator.  Tabulate  the  results: 

(1)  Titration c.c.  NaOH 

(2)  Titration c.c.  NaOH 

Average c.c.  NaOH 

Calculate  how. much  calcium  carbonate  would  be  required  to 
neutralize  the  soil. 


EXERCISE  74 

FERTILIZERS 

Object:     To  test  the  effect  of  certain  fertilizers  on  crops. 
Apparatus:  Large  jars. 

Materials:  Ammonium  nitrate.    Monocalc'um  or  disodium  phos- 
phate.   Potassium  sulphate.    Soil.    Seeds. 

a.  Essential  Plant-foods.    Nitrogen:  Dissolve  80  g.  of  am- 
monium nitrate  in  2500  c.c.  of  distilled  water.    Phosphorus: 
Dissolve  25  g.  of  monocalcium  phosphate,  or  26  g.  of  disodium 
phosphate  in  2500  c.c.  of  distilled  water.     Potassium:  Dissolve 
50  g.  of  potassium  sulphate  in  2500  c.c.  of  distilled  water.     Pre- 
pare these  solutions  carefully,  using  chemically  pure  salts,  and 
label  each  bottle. 

b.  Pot-culture  Test  for  Plant-food  Requirements.   Procure 
sufficient  of  a  poor  quality  of  soil  to  fill  eight  ordinary  four- 
gallon  butter  jars.     In  the  center  of  each  pot  make  a  drainage 
hole  about  ^  inch  in  diameter,  cover  this  with  a  copper-wire 
netting,  and  place  upon  this  a  piece  of  glass  wool  extending  over 
the  hole.     Fill  each  pot  with  the  soil,  pressing  it  in  firmly. 

Plant  the  series  with  wheat,  oats,  or  other  suitable  crop. 
Remove  the  surface  layer,  distribute  the  seed,  and  return  the 
soil  removed.  Use  sufficient  seeds  so  that  a  uniform  number  of 
strong  seedlings  may  be  left  in  the  pot  (about  20  seeds).  Place 
the  pots  either  in  a  greenhouse,  or  in  the  open,  but  so  that  they 
will  be  protected  from  severe  wind  or  heavy  rain.  Water  regu- 
larly. 

To  the  first  pot  add  no  fertilizer.     To  the  remaining  pots  add, 


96  FERMENTATION 

at  the  time  of  planting,  and  weekly  thereafter,  10  c.c.  of  the 
prepared  solutions,  as  follows: 

Pot  2.  Ammonium  nitrate. 

Pot  3.  Phosphate  solution. 

Pot  4.  Potassium  sulphate. 

Pot  5.  Ammonium  nitrate  and  phosphate  solution. 

Pot  6.  Ammonium  nitrate  and  potassium  sulphate. 

Pot  7.  Phosphate  solution  and  potassium  sulphate. 

Pot  8.  All  three  solutions. 

c.  When  mature,  the  ,crop  should  be  harvested  uniformly,  and 
weighed.  Afterwards,  separate  the  grain  from  the  straw,  and 
weigh  the  grain.  Calculate  the  yields  secured,  on  the  acre  basis. 

EXERCISE  75 

FERMENTATION 

Object :  To  ferment  some  molasses  and  to  study  some  of  the  properties 
of  alcohol. 

Apparatus:  Large  bottle  (2  1.)  or  flask,  1-hole  stopper  to  fit,  with 
L-tube,  delivery  tube  and  glass  tube.  Distillation  apparatus 
(Fig.  11,  Ex.  11).  Wide-mouth  bottle.  Mortar. 

Materials:  Molasses.  Yeast.  Limewater.  Litmus  papers.  As- 
bestos wool.  Sodium  hydroxide  (sol.).  Iodine. 

a.  Mix  250  c.c.  of  molasses  with  1500  c.c.  of  water  in  a  bottle 
or  large  flask.  Break  up  a  cake  of  yeast,  shake  it  with  water 
until  it  is  completely  suspended,  and  add  it  to  the  molasses. 
Plug  the  mouth  of  the  bottle  loosely  with  cotton,  and  set  the 
whole  in  a  warm  place  for  several  days.  This  quantity  will  serve 
for  10-15  students.  For  individual  experiments,  take  one-tenth 
of  the  above  amounts. 

6.  Fit  to  the  bottle  a  1-hole  stopper,  L-tube,  and  rubber  tube, 
terminating  in  a  straight  glass  tube.  Take  15  c.c.  of  limewater 
in  a  test-tube,  insert  the  glass  tube  to  the  bottom  of  this,  and 
shake  the  fermented  liquid  round  in  the  bottle  (?).  Note  the 
gas  evolved  and  its  reaction  with  limewater  (?).  In  what  form 
of  solution  was  the  gas  before  shaking? 

c.  Filter  off  100  c.c.  of  the  fermented  liquid,  place  it  in  a  flask 
and  distil  as  in  Fig.  11,  Ex.  11  a.  After  30  c.c.  has  come  over, 
empty  and  wash  the  flask,  and  re-distil  the  distillate  until  6-8 
c.c.  has  come  over. 


fM* 


ACETIC  ACID  97 

Note  the  odor  of  the  distillate  (?).  Test  it  with  litmus  papers 
(?).  Saturate  a  tuft  of  asbestos  wool  with  the  liquid,  set  the 
tuft  on  the  base  of  the  stand,  and  apply  a  light  (?).  Hold  a  cold, 
wide-mouth  bottle  over  the  flame,  to  recognize  one  product  (?). 
Close  the  bottle  and  test  the  gas  in  the  bottle  by  shaking  with 
limewater  (?).  Make  the  equation  for  the  combustion  (?).  If 
you  burned  alcohol  vapor  and  pure  oxygen,  what  relative  volumes 
should  you  use,  and  what  relative  volumes  of  the  products 
(measured  as  gases)  would  be  formed? 

d.  To  a  few  drops  of  the  alcohol  add  1  c.c.  of  sodium  hydrox- 
ide solution.     Pulverize  one  or  two  (not  more)  crystals  of  iodine, 
add  a  part  of  the  powder  to  the  mixture  and  warm  (?).     The 
amount  added  must  not  be  sufficient  to  give  a  permanent  brown 
tint  to  the  liquid.    The  precipitate  is  iodoform  CHI3  (related  to 
chloroform  CHC13). 

e.  Summarize  the  observed  physical  and  chemical  properties 
of  alcohol  (?). 

EXERCISE  76 
ACETIC  ACID 

Object:  To  observe  the  properties  of  acetic  acid,  the  difference  between 
a  strong  and  a  weak  acid,  and  the  liberation  of  acetic  acid  from 
an  acetate. 

Apparatus:  Test-tubes. 

Materials:  Acetic  acid  (dil.  6  N).  Sulphuric  acid  (dil.).  Zinc 
(dust)..  Sodium  acetate.  Litmus  papers. 

a.  Acetic  Acid.     Take  5  c.c.  of  acetic  acid  and  note  its  odor 
(?).     Test  it  with  litmus  papers  (?). 

To  show  that  acetic  acid  is  a  weak  acid  [189],  take  15  c.c. 
of  water  in  each  of  two  test-tubes.  To  one  add  the  5  c.c.  of 
acetic  acid  and  to  the  other  add  an  equal  volume  (5  c.c.)  of 
dilute  sulphuric  acid.  Add  a  little  zinc  dust  to  the  contents  of 
each  tube,  and  compare  (?).  Which  reaction  goes  faster? 

If  acetic  acid  had  been  added  to  the  starch  (Ex.  72  a)  or  sucrose 
(Ex.  72  d),  instead  of  hydrochloric  acid  (a  very  active  acid),  what 
change  in  the  procedure  would  have  been  necessary  to  get  the 
same  result? 

b.  To  about  0.5  c.c.  of  sodium  acetate  add  2  c.c.  of  water  and 
1  c,c.  of  concentrated  sulphuric  acid.    Warm  and  note  the  odor 


98  DESTRUCTIVE  DISTILLATION 

(?).    Test  the  vapor  with  litmus  papers  (?).     Make  the  equa- 
tion, assuming  that  the  second  product  is  NaHS04  (?). 
c.  Summarize  the  properties  of  acetic  acid  (?). 

EXERCISE  77 
DESTRUCTIVE  DISTILLATION  OF  WOOD  AND  COAL 

Object:  To  study  the  products  obtained  by  distilling  wood  and  coal, 
such  as  charcoal,  coke,  illuminating  gas,  etc. 

Apparatus:  Test-tube  (hard  glass),  tubing,  large  test-tubes  and 
beaker.  Glass  rod. 

Materials:  Sawdust  and  wood  c'hips.  Litmus  papers.  Bitu- 
minous coal  (crushed).  Lead  nitrate  (sol.).  Filter  paper. 

a.  Wood.  Take  three-fourths  of  a  hard  glass  test-tube  full 
of  sawdust  and  wood  chips.  Arrange  the  apparatus  as  in, Fig.  21. 
The  test-tube  is  inclined  slightly  downwards 
towards  the  mouth.  The  wide  test-tube,  in 
which  the  distillate  is  to  be  caught,  is  surrounded 
by  cold  water,  and  a  nozzle  is  inserted  in  one  of 
the  holes  in  the  stopper. 

Heat  the  contents  of  the  test-tube,  at  first 
gently,  and  later  strongly,  until  no  more  vapors 
are  evolved. 

b.  During  the  heating,  set  fire  to  the  issuing 
gas  (?).     Is  the  flame  luminous,  or  not?     Com- 
pounds of  what  element  must  be  present? 

c.  Examine    the    condensed    liquid.      What 


FIG.  21         liquid  or  liquids  are  seen?     Test  the  liquid  with 
litmus  papers  (?).     What  dissolved  substance 
causes  this  reaction  [420]? 

d.  Examine,  describe,  and  name  the  residue  in  the  hard  glass 
test-tube  (?).    Place  it  in  a  corked  test-tube  for  use  in  Ex.  78. 

e.  Name  five  observed  products  from  distilling  wood  (?). 

/.  Coal.  Charge  a  hard  glass  test-tube  with  crushed  soft 
coal,  attach  a  clean  test-tube  to  catch  the  distillate,  and  repeat 
a  [423]. 

g.  To  test  for  hydrogen  sulphide  in  the  coal  gas,  dip  a  glass 
rod  in  lead  nitrate  solution,  wipe  it  on  a  small  piece  of  filter  paper, 
and  hold  the  latter  in  the  unlighted  gas  (?).  What  compound 
is  formed  on  the  paper  [263  and  Ex.  40  c]. 


WOOD  CHARCOAL  AND  BONE  BLACK  99 

h.  Repeat  b  and  c. 

j.  Examine  and  name  the  residue  (?). 

k.  Name  six  observed  products  from  distilling  coal  (?). 

EXERCISE  78 
WOOD  CHARCOAL  AND  BONE  BLACK 

Object:   To  study  the  properties  of  wood  charcoal  and  of  bone  black. 

Apparatus:   Iron  wire.     Test-tubes.     Crucible  (porcelain). 

Materials:  Charcoal  (splinters).  Splints.  Litmus  (sol.).  Wood 
charcoal  (powdered).  Bone  black.  Molasses.  Cupric  sulphate 
(sol.).  Ferrous  sulphide.  Sulphuric  acid  (dil.). 

a.  Charcoal.    Light  first  a  splinter   of   wood  and  then  a 
splinter  of  charcoal  in  the  flame  (?).     Describe  how  each  burns 
(?).    What  is  the  cause  of  the  flame  in  one  case  (?),  and  of  the 
absence  of  flame  in  the  other  (?)  ? 

b.  Place  a  splinter  of  charcoal  in  a  test-tube  half-filled  with 
water.     Is  charcoal  heavier  or  lighter  than  water? 

Hold  the  splinter  of  charcoal  under  the  water  by  means  of  an 
iron  wire,  one  end  of  which  is  twisted  round  it,  and  boil  the  water 
for  five  minutes.  Remove  the  wire  from  the  splinter.  Does  the 
latter  now  sink  or  float?  Is  carbon  specifically  lighter  or  heavier 
than  water?  Why  is  fresh  charcoal  lighter  [421]? 

c.  To  a  test-tube  half  full  of  water  add  two  or  three  drops  of 
litmus  solution.    Add  about  4  c.c.  of  powdered  charcoal,  boil 
for  five  minutes,  and  filter.    Where  is  the  litmus?    What  class 
of  substances,  especially,  is  adsorbed  by  charcoal  from  solutions 
[4221? 

d.  Bone  Black  [438].    Heat  about  15  c.c.  of  bone  black  in 
the  crucible  (covered).    The  purpose  of  the  heating  is  to  make 
the  charcoal  more  active  by  driving  out  gases  and  moisture 
already  adsorbed  on  the  surfaces  of  its  pores. 

Take  two  test-tubes  half  filled  with  water,  and  add  to  one 
enough  molasses  to  confer  a  distinct,  tint,  and  to  the  other  a  few 
drops  of  cupric  sulphate  solution. 

When  the  bone  black  has  cooled,  put  about  4  c.c.  of  it  in 
each  test-tube,  and  shake  vigorously. 

Filter  the  dilute  molasses.  If  the  filtrate  is  still  colored  (?), 
pour  it  through  the  filter  again.  Taste  the  filtrate  (?).  Filter 
the  dilute  cupric  sulphate,  and  examine  the  filtrate  (?). 


100  TESTS  FOR  FOOD  COMPONENTS 

What  difference  do  you  observe?  Was  the  sugar  removed, 
or  only  the  coloring  matter?  Explain  (?).  What  commercial 
use  is  made  of  this  property  of  bone  black  [402]? 

e.  Place  in  a  test-tube  a  small  piece  of  ferrous  sulphide,  10  c.c. 
of  water  and  5  c.c.  of  dilute  sulphuric  acid.  Note  the  odor  (?) 
and  name  the  gas  (?).  When  the  action  is  well  started,  decant 
the  liquid  to  a  clean  test-tube,  add  the  rest  of  the  heated  bone 
charcoal  (from  d),  shake  vigorously,  and  note  the  odor  (?). 
What  property  is  here  illustrated? 

EXERCISE  79 
TESTS  FOR  FOOD  COMPONENTS 

Object:  To  learn  some  tests  for  starch,  glucose,  milk-sugar,  proteins, 
and  fats,  and  to  apply  them  to  two  common  foods.  Incidentally,  to 
show  that  starch  is  partly  digested  by  saliva  during  mastication. 

Apparatus :  Test-tubes.     Evaporating  dish. 

Materials:  Starch.  Iodine  (sol.  in  KI).  Glucose  (solid).  Feh- 
ling's  solution  (Nos.  I  and  II).  Milk-sugar.  Egg  albumen. 
Nitric  acid  (cone.).  Ammonium  hydroxide.  Woolen  yarn. 
Fat.  Cottonseed  oil.  Almonds  (crushed).  Meat.  Sausage. 
Carbon  tetrachloride. 

a.  Starch.    Place  water  in  a  test-tube,  add  a  pinch  of  starch, 
shake,  and  boil  (?).    How  does  the  starch  change?    Cool  the 
suspension  in  running  water,  and  when  it  is  cold  (not  before), 
divide  it  into  two  parts  and  to  one  add  a  drop  of  the  solution  of 
iodine  in  potassium  iodide  (?).     Keep  the  other  half  for  use  in  e 

b.  Take  another  pinch  of  dry  starch,  and  add  to  it  a  few  drops 
of  the  iodine  solution  (?).    Tabulate  the  results  of  a  and  b,  as 
well  as  those  of  c,  d, /,  and  g,  as  follows: 

FOOD  COMPONENT  REAGENT  OR  TREATMENT         RESULT 

Starch  (suspension)  Iodine  sol. 

Starch  (grains)  Iodine  sol.  ? 

c.  Glucose.    Shake  about  0.5  c.c.  of  glucose  in  5  c.c.  of  water. 
Add  5  c.c.  of  Fehling's  solution  (Ex.  72,  footnote)  and  boil  (?). 

d.  Lactose   (milk-sugar):  Repeat  c  with  about  0.5  c.c.  of 
milk-sugar  (?). 

e.  Maltose  from  Starch.      To  5  c.c.  of  the  starch  suspension 
prepared  in  a  (which  itself  gives  no  reaction  with  Fehling's  solu- 


FOOD  COMPONENTS  OF  MlLK  101 

tion,  Ex.  72  a),  add  about  1  c.c.  of  saliva,  mix,  and  set  aside  for 
fifteen  minutes.  Then  add  5  c.c.  of  Fehling's  solution  and  boil 
(?).  How  was  the  maltose  produced  [430]? 

/.  Protein.  To  a  few  particles  of  egg  albumen,  add  a  few 
drops  of  concentrated  nitric  acid  (?).  Add  some  water  to  wash 
off  the  acid,  and  pour  away  the  liquid,  leaving  the  solid  residue. 
To  the  latter  add  a  few  drops  of  ammonium  hydroxide  (?). 

Repeat  with  a  scrap  of  woolen  yarn  (?). 

Account  for  the  effect  of  nitric  acid  on  the  skin  and  nails  (?). 

g.  Fat.  Place  on  small  pieces  of  unglazed  paper  (1)  a  par- 
ticle of  fat,  (2)  a  drop  of  cottonseed  oil,  and  (3)  part  of  a  crushed 
almond;  put  them  in  the  evaporating  dish,  and  warm  gently 
until  the  fat  melts.  Examine  the  papers  (?). 

h.  Examination  of  a  Food.  Rub  a  small  piece  of  raw  meat 
in  the  mortar  with  a  little  water  until  the  color  is  removed. 
Then  apply  to  portions  of  the  meat  the  tests  in  a  for  starch  (?) , 
in/ for  protein  (?),  and  in  g  for  fat  (?). 

j.  Take  a  small  piece  of  sausage  and  apply  to  portions  of  it 
the  tests  in  a,  /,  and  g.  If  the  results  of  a  and  /  are  not  definite, 
dissolve  away  the  fat  by  shaking  the  fragments  of  sausage  with 
carbon  tetrachloride,  and  try  a  and/  again  with  the  residue  (?). 


EXERCISE  80 
FOOD  COMPONENTS  OF  MILK 

Object:  To  find  the  food  components  present  in  milk.  To  explain 
curdling.  To  learn  a  test  for  a  common  preservative,  formaldehyde. 

Apparatus:  Evaporating  dish.    Test-tubes.    Glass  rod. 

Materials:  Milk.  Nitric  acid  (cone.).  Ammonium  hydroxide. 
Acetic  acid.  Fehling's  solution  (Nos.  I  and  II).  Litmus 
papers.  Iodine  (sol.  in  KI).  Formaldehyde  (1%  sol.).  Sul- 
phuric acid  (cone.).  Ferric  chloride  (sol.). 

a.  Heat  50  c.c.  of  milk  to  boiling  in  the  evaporating  dish. 
With  a  glass  rod,  fish  out  the  skin  which  forms  on  the  surface 
and  transfer  it  to  a  test-tube.  Apply  to  it  the  test  in  Ex.  79  / 
for  protein  (?).  Name  the  substance  [429]. 

To  the  milk  add  three  or  four  drops  of  acetic  acid  and  stir  (?). 
How  is  this  result  to  be  classified?  What  sort  of  substances 
cause  milk  to  curdle?  What  is  the  connection  with  "sour 


102  FOOD  COMPONENTS  OF  FLOUR 

milk"?    Filter  the  acidified  milk  and  test  the  residue  on  the 
filter  for  protein  (?). 

b.  To  5  c.c.  of  the  filtrate  add  5  c.c.  of  Fehling's  solution, 
and  boil  (?).     What  is  shown  to  be  present  (Ex.  79  d)? 

c.  To  5  c.c.  of  the  filtrate  from  a  add  iodine'  solution  (?). 
For  what  food  component  is  this  a  test?    Is  it  present? 

d.  Put  a  few  drops  of  unboiled  milk  on  a  piece  of  unglazed 
paper  and  heat  as  in  Ex.  79  g  (?).    Result? 

e.  Which  food  components  have  you  found  in  milk? 

/.  Preservative  —  Formaldehyde.  To  5  c.c.  of  milk  in  a 
test-tube  add  an  equal  volume  of  water  and,  by  means  of  a  glass 
rod,  one  drop  (not  more)  of  formaldehyde  solution  and  shake. 
Take  5  c.c.  of  concentrated  sulphuric  acid  and  add  to  it  by  a 
glass  rod  one  drop  of  ferric  chloride  solution.  Now  hold  the 
test-tube  of  milk  almost,  but  not  quite  vertical,  and  pour  the 
sulphuric  acid  in  a  continuous  stream  down  the  side  of  the  tube 
so  that  it  may  go  to  the  bottom  and  form  a  layer  under  the  milk. 
What  color  appears  where  the  liquids  meet?  Repeat  with  di- 
luted milk  free  from  formaldehyde  (?). 

EXERCISE  81 
FOOD  COMPONENTS  OF  FLOUR 

Objects :   To  find  the  food  components  in  wheat  flour. 
Apparatus :  Evaporating  dish.     Test-tubes.     Beaker. 
Materials:  Flour.     Cheesecloth  (squares).     Thread.     Iodine  (sol. 

in  KI).     Fehling's  solution  (Nos.  I  and  II).     Nitric  acid  (cone.). 

Ammonium  hydroxide. 

a.  Take  about  10  c.c.  of  flour,  make  it  into  a  dough  with 
water,  and  then  place  it  in  a  small  piece  of  cheesecloth.    Bring 
the  corners  together  and  with  a  thread  tie  the  cloth  so  as  to 
enclose  the  dough  in  a  bag. 

Knead  the  bag  in  water  in  the  evaporating  dish  so  long  as 
the  liquid  squeezed  out  appears  to  be  more  milky  than  that 
in  the  dish.  Then  pour  the  milky  liquid  into  a  beaker  to  settle. 

Open  out  the  cloth  and  wash  the  contents  in  running  water 
until  the  wash-water  is  no  longer  milky. 

b.  Test  portions  of  the  residue  in  the  cloth  for  starch  (?), 
glucose  (?),  and  protein  (?),  and  record  the  results  (?). 

c.  Test  a  pinch  of  the  dry  flour  for  fat  (?). 


ANALYSIS  OF  BAKING  POWDER  103 

d.  Pour  the  water  away  from  the  sediment  in  the  beaker 
(from  a)  and  test  portions  of  the  solid  for  starch  (?),  glucose  (?), 
and  protein  (?),  and  record  the  results  (?). 

e.  Summarize  the  food  components  found  in  flour  (?). 


EXERCISE  82 

ANALYSIS  OF  BAKING  POWDER 

(Qualitative) 

Object:  Baking  powders  contain  sodium  bicarbonate,  a  substance 
which  is  acid  (or  becomes  so  on  being  heated),  and  starch  to  delay 
interaction.  The  acid  (or  acid-forming)  substance  may  be  potas- 
sium Mtartrate  KHC^H^O^,  or  calcium  acid  phosphate  Ca(H2P04)2, 
or  potassium  bisulphate  KHSO*,  or  ammonium  alum  ( NH^ySO*, 
Ak(S0^3,24:H^).  The  object  is  to  learn  tests  for  the  presence  of 
the  radicals  of  these  substances. 

Apparatus:  Test-tubes.  Funnel.  Evaporating  dish.  Platinum 
wire. 

Materials:  Baking  powder.  Filter  paper.  Sulphuric  acid  (cone.) 
Nitric  acid  (dil.).  Ammonium  molybdate  (sol.,  Ex.  55).  Hy- 
drochloric acid  (dil.).  Barium  chloride  (sol.).  Sodium  hy- 
droxide (sol.).  Litmus  papers.  Ammonium  hydroxide  (sol.). 
Acetic  acid  (dil.,  6  AT).  Ammonium  oxalate  (sol.).  Iodine  (sol. 
in  KI).  Cobalt  chloride  (sol.). 

a.  Preparatory.    Place  about  4  c.c.  of  the  baking  powder 
into  a  large  test-tube,  add  20  c.c.  of  water,  and  shake  vigorously 
for  several  minutes.     Filter  the  liquid  and  test  the  clear  filtrate 
as  in  c,  d,  e,  and  /. 

b.  Starch  (see  Ex.  72  b).    Perforate  the  filter  paper  and  with 
water  wash  some  of  the  residue  into  a  test-tube.    Boil  this  sus- 
pension, and  then  cool  it  and  fill  the  test-tube  up  with  water. 
With  a  glass  rod,  add  to  the  suspension  one  drop  of  the  iodine 
solution  (?).    A  blue  color  indicates  starch. 

c.  Tartrate  Radical.     Place  4  c.c.  of  the  filtrate  (a)  in  an 
evaporating  dish  with  5  drops  of  concentrated  sulphuric  acid 
and  evaporate  to  dryness  over  a  small  flame.     Charring  and 
an  odor  of  burnt  sugar  indicate  a  tartrate. 

d.  Phosphate  Radical  (see  Ex.  55  b).    Take  1  c.c.  of  the  fil- 
trate (a)  and  acidify  with  1  c.c.  of  dilute  nitric  acid.    To  5  c.c. 


104  ESTERS.    SOAP 

of  ammonium  molybdate  solution  add  3  drops  of  this  mixture, 
warm,  and  set  in  the  rack  (?).  Phosphates  give  a  yellow  pre- 
cipitate. 

e.  Sulphate  Radical  (see  Ex.  47  d).  Acidify  about  5  c.c.  of 
the  filtrate  (a)  with  5  c.c.  of  dilute  hydrochloric  acid  and  add 
barium  chloride  solution  (?).  What  is  the  precipitate  (if  any)? 

/.  Ammonium  Radical  (Ex.  51  /).  To  5  c.c.  of  the  filtrate  (a) 
add  5  c.c.  of  sodium  hydroxide  solution.  Heat  to  boiling  and 
note  the  odor  (?)  and  reaction  of  the  vapor  (not  the  liquid) 
towards  moist  red  litmus  paper  (?).  What  is  the  gas  (if  any)? 

g.  Calcium  Radical.  Shake  about  0.5  c.c.  of  the  baking  pow- 
der with  5  c.c.  of  dilute  hydrochloric  acid.  Filter  and  to  the 
filtrate  add  ammonium  hydroxide  until  the  liquid  is  alkaline 
to  litmus.  Now  add  acetic  acid  until  the  solution  is  acid  to 
litmus,  boil,  and  filter  if  the  liquid  is  not  clear.  Add  ammonium 
oxalate  solution.  The  precipitate,  if  any,  is  calcium  oxalate. 

h.  Aluminium  Radical.    For  test,  see  Exercise  95  a. 

j.  Report.  Summarize,  stating  which  radicals  were  present 
and  which  absent  (?) 


EXERCISE  83 
ESTERS.    SOAP 

Object:  To  learn  the  nature  of  fats  (which  are  esters)  by  forming 
and  decomposing  a  simple  ester.  To  make  soap  and  observe  its 
properties. 

Apparatus:  Test-tubes.  Evaporating  dish.  Glass  rod.  Trip 
scales. 

Materials:  Sodium  acetate.  Alcohol  (95%).  Sulphuric  acid 
(cone.).  Amyl  alcohol  (or  fusel  oil).  Methyl  acetate.  Litmus 
papers.  Fat  or  cottonseed  oil.  Sodium  hydroxide.  Hydro- 
chloric acid  (dil.).  Sodium  hydroxide  (sat.  sol.).  Sodium 
chloride  (sol.). 

a.  Formation  of  an  Ester.  To  1  c.c.  of  sodium  acetate  in  a 
test-tube  add  2  c.c.  of  alcohol  and  1  c.c.  of  concentrated  sul- 
phuric acid.  Agitate  for  a  minute  or  two,  warm  very  slightly 
(do  not  boil!),  and  note  the  odor  [349]  (?).  This  is  a  test  for 
acetic  acid  or  an  acetate.  Write  the  equation  (?),  and  name 
each  substance  (?). 


COLLOIDAL  SUSPENSIONS  105 

b.  Repeat,  using  amyl  alcohol  instead  of  ordinary  alcohol  (?). 

c.  Hydrolysis  of  an  Ester.    Place  10  c.c.  0%  water  in  one 
test-tube  and  0.5  c.c.  of  methyl  acetate  CH3(CO2CH3)  in  an- 
other.    Test  each  with  blue  litmus  paper  (?),  then  mix  and  test 
again  [433]  (?).     If  the  result  is  not  definite,  wait  a  few  minutes 
and  test  the  mixture  once  more.    Write  the  equation  (?),  and 
name  each  substance  (?). 

cL  Saponification  of  an  Ester:  Soap  Making.  Mix  in  a  test- 
tube  5  c.c.  of  cold,  saturated  sodium  hydroxide  solution  and  5  c.c. 
of  alcohol,  shake,  and  allow  to  settle  (?).  Pour  off  the  upper 
alcoholic  layer  into  another  test-tube,  add  to  it  an  equal  volume 
of  fat  or  cotton  seed  oil,  and  shake  (?).  Put  the  liquid  into  an 
evaporating  dish  on  the  wire  gauze  and  set  fire  to  the  contents. 
Warm  the  dish  with  a  very  small  flame  to  assist  in  driving  off 
the  alcohol.  Stir  until  the  flame  goes  out,  and  then  stop  heating. 
The  pasty  mass  is  soap,  mainly  sodium  st  ear  ate  and  sodium 
palmitate  [438],  mixed  with  glycerine.  Write  an  equation  (?). 
Rub  a  little  with  water  in  the  hands  (?). 

The  alcohol  is  used  simply  as  a  common  solvent  for  the  fat  and 
the  alkali  and  is  employed  in  the  laboratory  experiment  to  save 
time. 

e.  Dissolve  the  soap  (e)  in  a  little  warm  distilled  water  and 
cool.  To  half  of  the  solution  in  a  test-tube  add  hydrochloric 
acid  and  shake  vigorously  [440]  (?). 

To  show  that  the  precipitate  is  an  acid,  withdraw  it  by  means 
of  a  glass  rod,  suspend  it  in  10  c.c.  of  water  in  another  test-tube, 
add  a  few  drops  of  sodium  hydroxide  solution  and  heat  until 
solution  takes  place.  Write  the  equation  (?). 

To  what  class  of  substances  does  /  show  soap  to  belong? 

/.  To  the  other  half  of  the  cold  soap  solution,  add  sodium 
chloride  solution  (?).  This  is  called  " salting  out"  [439],  and 
is  a  case  of  coagulating  a  colloid  [442].  To  what  class  of  solu- 
tions does  this  show  soap  solution  to  belong? 

EXERCISE  84 
COLLOIDAL  SUSPENSIONS 

Object:   To  prepare  a  colloidal  suspension,  and  observe  its  properties. 
Apparatus:   Test-tubes.      Funnel.      Square    bottle    (20-25    c.c.). 
Optional:  300  c.c.  beaker. 


106  COLLOIDAL  SUSPENSIONS 

Materials:  Arsenic  trioxide.  Filter  paper.  Hydrogen  sulphide 
(sol.).  Sodium  chloride  (sol).  Hydrochloric  acid  (cone.). 
Calcium  chloride  (sol.).  Sugar.  Rosin.  Alcohol  (95%  or 
denatured). 

Optional:  Ferric  chloride  (sol.  5%).    Sodium  sulphate  (sol.). 
Sodium  carbonate  (sol.). 

a.  Preparation.    Shake  some  arsenic  trioxide  with  25  c.c.  of 
cold  water  vigorously  for  several  minutes,  filter,  and  to  the  filtrate 
add  an  equal  volume  of  hydrogen  sulphide  solution.    Arsenious 
sulphide  As2S3  is  formed,  but  remains  in  colloidal  suspension. 

b.  Optical  Examination.     Pour  the  suspension  into  a  square 
bottle,  and  examine  it  in  sunlight,  or,  better  still,  by  holding  it 
close  to  an  incandescent  bulb.    Look  first  through  it  towards 
the  light  (?).    Does  it  appear  to  be  transparent  and  clear,  or 
no?  Now  look  at  it  from  a  position  at  right  angles  to  the  direc- 
tion of  the  light,  and  answer  the  same  question  (?).     With  a 
microscope,  the  particles  in  such  solutions  can  be  perceived,  in- 
dividually [441]. 

c.  Coagulation.    Divide  the  *  solution  between  5  clean  test- 
tubes.    Keep  one,  corked,  for  reference.    To  one  add  sodium 
chloride  solution  (?),  to  another  dilute  hydrochloric  acid  (?), 
to  the  third  calcium  chloride  solution  (?),  dissolve  a  little  sugar 
in  the  fourth  (?),  and  observe  them  from  tune  to  time.    Note 
which  coagulates  last  (?).  ^ 

The  positive  ion  is  here  the  coagulating  agent.  How  does 
valence  affect  coagulating  power?  Do  non-ionized,  non-col- 
loidal substances  like  sugar  produce  coagulation? 

After  a  day  or  two,  does  the  arsenious  sulphide  hi  the  refer- 
ence test-tube  coagulate  or  settle  of  its  own  accord? 

d.  Colloidal  Rosin.      Dissolve  a  single  particle  of  rosin  in 
1  c.c.  of  alcohol.    Add  the  solution  to  a  test-tube  full  of  water 
(?).    Examine  in  the  light  as  in  6  (?).    Cork  and  keep,  to  see 
whether  settling  takes  place  (?). 

e.  Summarize   the   special   properties   of    colloidal    suspen- 
sions (?). 

/.  Colloidal  Ferric  Hydroxide  (optional).  Boil  300  c.c.  of 
distilled  (or  soft)  water  in  a  large  beaker,  and  add  to  it,  a  few 
drops  at  a  time,  3  c.c.  of  ferric  chloride  solution.  The  salt  is  thus 
somewhat  hydrolyzed  and  contains  suspended  ferric  hydroxide 
Fe(OH)3  (color  ?). 


HOW  SOAP  CLEANSES  107 

Examine  this  suspension  in  the  light  as  in  b  (?). 

Take  5  test-tubes  full  of  the  prepared  liquid,  keep  one  for 
reference,  and  add  to  each  of  the  others  a  very  dilute  solution  of 
one  of  the  following  coagulants:  sodium  chloride,  sodium  sul- 
phate, sodium  carbonate,  calcium  chloride.  This  colloid  is 
coagulated  by  the  negative  ion.  Note  the  time  required  in  each 
case  (?).  What  is  the  effect  of  valence? 

EXERCISE  85 
How  SOAP  CLEANSES 

Object:  To  observe  the  power  of  soap  solution  to  produce  an  emulsion, 
and  to  clean  a  test-tube  brush,  covered  with  oil  and  rust,  separating 
the  rust  and  oil  from  one  another  as  well  as  from  the  brush. 

Apparatus:  Test-tubes.  Beaker  (100  c.c.).  Flask.  Test-tube 
brush. 

Materials:  Kerosene.  Cottonseed  oil.  Ivory  soap  (sol.  1  :10, 
hot).  Suspension  of  ferric  oxide  (powdered)  in  cottonseed  oil 
(6  g.  in  100  c.c.  for  whole  class). 

a.  Place  1  c.c.  of  kerosene  in  one  test-tube  and  1  c.c.  of  cotton- 
seed oil  in  another.    Add  about  10  c.c.  of  water  to  each,  shake 
vigorously  and  place  in  the  rack  (?).    Is  a  permanent  emulsion 
formed? 

Now  add  to  each  2  c.c.  of  soap  solution,  shake  again,  and 
observe  as  before  (?). 

b.  Boil  200  c.c.  of  water  in  a  flask.    Saturate  the  test-tube 
brush  with  the  rust  suspended  in  oil  and  push  it  into  a  test-tube. 
Add  about  15  c.c.  of  the  hot  water,  and  work  the  brush  in  the 
tube  (?).     Does  hot  water  alone  remove  the  rust  and  oil? 

Remove  the  brush,  pour  out  the  water,  place  15  c.c.  of  hot 
soap  solution  in  the  test-tube,  and  work  the  brush  in  the  tube 
as  before  (?).  Remove  the  brush,  pour  the  contents  of  the  test- 
tube  into  a  100  c.c.  beaker,  and  rinse  first  the  brush  and  then  the 
test-tube  with  hot  water,  catching  the  rinsing-water  in  the 
beaker.  Have  the  oil  and  rust  been  removed  from  the  brush? 

After  a  short  time,  examine  the  contents  of  the  beaker  (?). 
Where  is  the  oil  (?)  and  in  what  condition?  Where  is  the  rust 
(?)  and  is  it  free  from  oil? 

Explain  how  soap  solution  removes  grease  or  oil  from  a  large 
object  or  a  powder  (?) 


108  COMPOUNDS  OF  MAGNESIUM 

EXERCISE  86 
COMPOUNDS  OF  MAGNESIUM 

Object:  To  study  the  preparation  of  compounds  by  double  decompo- 
sition, and  (in  d  and  e)  to  observe  the  properties  of  the  carbonate 
and  oxide  of  magnesium. 

Apparatus :   Test-tubes.     Glass  rod. 

Materials:  Magnesium  chloride.  Sodium  hydroxide  (sol).  So- 
dium carbonate  (sol.).  Ammonium  chloride  (sol.).  Ammonium 
hydroxide  (sol.).  Sodium  phosphate  (sol.).  Magnesium  car- 
bonate (powdered).  Limewater.  Hydrochloric  acid  fdil.). 

a.  Dissolve  about  0.5  c.c.  of  magnesium  chloride  (properties  ?) 
in  10  c.c.  of  water,  and  divide  the  solution  into  three  portions. 

To  one  portion  add  sodium  hydroxide  solution  (?).  Remem- 
ber that  salts,  bases,  and  acids  usually  interact  by  double  de- 
composition. On  this  basis,  write  the  equation  (?),  and  name 
each  substance  (?). 

b.  To  the  second  portion  (a)  add  sodium  carbonate  solution 
[447]   (?).     Why  does  the  addition  of  sodium  bicarbonate  to 
table  salt  containing  magnesium  chloride  prevent  the  salt  from 
becoming  moist  in  damp  weather? 

c.  Test.     To  the  third  portion  (a)  add  ammonium  chloride 
solution  (not  included  in  equation),  then  a  little  ammonium 
hydroxide  and  sodium  phosphate  (?).     Rub  the  inside  of  the 
test-tube  with  a  glass  rod  and  note  where  the  precipitate  appears 

(?) 

d.  Heat  0.5  c.c.  of  powdered  magnesium  carbonate  in  a  test- 
tube  and  lower  into  the  gas  a  rod  dipped  in  limewater  (?).    Write 
the  equation  (?).    Use  the  residue  —  after  strong  heating  — 
in  e. 

e.  To  the  residue  from  d,  when  cold,  add  dilute  hydrochloric 
acid  (?).    What  sort  of  oxide  is  magnesium  oxide? 

EXERCISE  87 
ALUMINIUM  HYDROXIDE.    ALUM 

Object:  To  prepare  a  double  sail  in  beautiful  crystals.  To  observe  the 
formation  of  aluminium  hydroxide,  and  its  properties  of  coagulating 
suspended  matter  and  forming  lakes  with  dyes. 

Apparatus:   Test-tubes  (Targe).    Glass  rod.    Trip  scales. 


DYEING  109 

Materials:  Ammonium  sulphate.  Aluminium  sulphate.  Thread. 
Aluminium  sulphate  (sol.).  Litmus  papers.  Limewater.  Am- 
monium hydroxide.  Clay. 

a.  Ammonium  Alum  —  a    Double    Salt.     Calculate    what 
weight  of  ammonium  sulphate  (NH4)2S04  is  required  to  give  as 
many  molecules  as  are  contained  in  10  g.  of  aluminium  sulphate 
[469]  (?).     Weigh  out  the  equivalent  quantities  of  the  two  salts, 
and  dissolve  them  separately,   each  in  the  smallest  possible 
amount  of  hot  water. 

Then  mix  the  clear  solutions,  suspend  a  thread  tied  to  a  glass 
rod  in  the  mixture,  and  set  it  aside  to  crystallize.  Note  the 
form  (?),  color  (?),  and  taste  (?)  of  the  crystals. 

b.  Aluminium  Hydroxide.    Dilute  2  c.c.  of  aluminium  sul- 
phate solution  with  20  c.c.  of  water. 

To  half  of  the  solution  add  about  15  c.c.  of  limewater  (?). 
Write  the  equation. 

To  the  other  half  add  ammonium  hydroxide  (?).  Equa- 
tion (?). 

c.  Coagulation.    Take  100  c.c.  of  water  with  clay  in  suspen- 
sion, add  1  c.c.  of  aluminium  sulphate  solution,  stir  vigorously, 
and  then  add  15  c.c.  of  limewater.     Observe  the  water  after  it 
has  stood  for  some  time  (?).    Explain  [470]  (?). 

d.  Lakes  [476].     Take  some  logwood  solution,  add  to  it  a  few 
drops  of  ammonium  hydroxide,  and  shake.     Then  add  1  c.c.  of 
aluminium  sulphate  solution,  shake,  and  allow  to  stand  (?). 

EXERCISE  88 
DYEING 

Object:  To  try  two  dyes,  one  of  which  dyes  cotton  directly,  while  the 
other  will  dye  it  only  with  the  help  of  a  mordant. 

Apparatus:  Evaporating  dish.  Graduated  cylinder.  Test-tubes. 
Glass  plate. 

Materials:  White  cotton  cloth  (pieces  5x2  cm.).  White  flannel 
(5x2  cm.).  Hydrochloric  acid  (cone.).  Ammonium  hydrox- 
ide. Chrysophenin  (suspension,  1%).  Sodium  sulphate  (sol., 
8  g.  Na2SO4,10H2O  per  liter).  Alizarin  (suspended,  5  g.  of  20% 
paste  to  100  c.c.  water).  Aluminium  sulphate  (sol.,  N). 

a.  Preparing  the  Cotton.  In  case  the  sizing  has  not  been 
removed  from  the  cotton  cloth,  boil  three  pieces  in  50  c.c.  of 


110  REACTIONS  OF  IRON  COMPOUNDS 

water  containing  2  c.c.  of  concentrated  hydrochloric  acid.  Rinse 
the  goods  in  water,  dip  in  50  c.c.  of  cold  water  containing  0.5  c.c. 
of  ammonium  hydroxide,  and  rinse  again. 

b.  Chrysophenin,  a  Direct  Dye  on  Both  Cotton  and  Wool. 
To  20  c.c.  of  water  in  the  evaporating  dish  add  5  c.c.  of  the 
chrysophenin  suspension  (shake  the  bottle)  and  1  c.c.  of  sodium 
sulphate  solution,  and  heat  to  boiling. 

Place  in  this  bath  one  piece  each  of  flannel  and  of  cotton  and 
keep  them  in  motion  with  a  glass  rod  for  two  minutes.  Remove 
them  and  wash  in  running  water  (?) .  Is  the  dye  fast  to  washing  on 
both?  What  was  the  purpose  of  the  sodium  sulphate  [476,  par.  2]? 

Smooth  out  the  samples  on  a  square  of  glass  (or  a  bottle)  to 
dry,  and  paste  them  in  your  note-book. 

c.  Alizarin,  a  Non-basic,  Mordant  Dye.  In  a  test-tube  dilute 
2  c.c.  of  aluminium  sulphate  solution  with  10  c.c.  of  water; 
place  in  it  a  piece  of  cotton  cloth  and  boil  for  two  minutes. 

In  a  second  test-tube  dilute  1  c.c.  of  ammonium  hydroxide 
with  10  c.c.  of  water.  Wring  the  piece  of  cloth,  place  it  in  this 
solution  and  warm  and  shake  for  two  minutes.  Then  wring  the 
cloth,  which  is  now  mordanted  with  aluminium  hydroxide. 

In  the  evaporating  dish  put  50  c.c.  of  water  and  5  c.c.  of  the 
alizarin  suspension  (shake  the  bottle).  Place  in  this  the  piece  of 
mordanted  cloth  and  a  piece  of  unmordanted  cotton,  and  heat 
to  boiling.  Keep  the  pieces  of  cloth  in  motion  for  at  least  ten 
minutes.  Finally,  wash  them  in  running  water  (?).  Is  the  dye 
fast  to  washing  on  both?  Why  do  they  differ?  % 

Dry  the  samples  on  glass  and  paste  them  into  the  note-book. 

EXERCISE  89 
REACTIONS  OF  IRON  COMPOUNDS 

Object:  To  try  the  tests  for  ferrous  and  ferric  salts,  and  to  learn  how 
ferrous  salts  are  changed  into  ferric  salts  by  oxidation  and  vice 
versa. 

Apparatus:  Test-tubes.  1-hole  stopper.  L-  and  delivery  tubes. 
Funnel. 

Materials:  Ferrous  sulphate.  Ferric  chloride  (sol.).  Potassium 
ferrocyanide  (sol.),  ferricyanide  (sol.),  and  thiocyanate  (sol.). 
Ferrous  chloride  (sol.).  Chlorine-water.  Ammonium  hydrox- 
ide. Ferrous  sulphide.  Hydrochloric  acid  (dil.).  Iron  (pow- 
dered). Filter  paper. 


REACTIONS  OF  IRON  COMPOUNDS  111 

a.  Tests  for  Ferrous  and  Ferric  Salts.    Wash  some  crystals 
of  ferrous  sulphate  in  water  until  the  surface  layer  has  been 
removed  by  solution.     Dissolve  them  in  15  c.c.  of  water  and 
divide  into  three  parts. 

Dilute  5  c.c.  of  ferric  chloride  solution  with  10  c.c.  of  water 
and  divide  into  three  parts. 

Test  each  of  the  salts  with  the  three  following  reagents  and 
tabulate  the  results: 

POTASSIUM  POTASSIUM  POTASSIUM 

FERKOCYANIDE  FEBBICYANIDB  THIOCYANATE 

Ferrous: 
Ferric: 

In  the  table,  note  the  color  produced  (?),  and  whether  there 
is  a  precipitate  or  simply  a  colored  solution  (?). 

Write  the  equations  for  the  interactions  with  the  ferric  salts 
[497-8]  (?).  Potassium  thiocyanate  is  K(CNS). 

Give  one  distinctive  test  for  a  ferrous  salt  (?)  and  two  for  a 
ferric  salt  (?). 

b.  Oxidation  of  Ferrous  Compounds.     To  a  solution  of  fer- 
rous chloride  add  an  oxidizing  agent  [219]  such  as  chlorine-water, 
hydrogen  peroxide  (acidified),  or  bromine  water.     Then  test  for 
ferric-ion,  using  tests  from  a.    What  change  has  the  ferrous-ion 
undergone?  4 

c.  Boil  some  water  in  a  test-tube  to  remove  dissolved  oxygen, 
and  cool  in  running  water.    Wash  off  the  surface  layer  from  a 
crystal  of  ferrous  sulphate,  and  dissolve  it  in  the  boiled  water. 
Now  add  a  few  drops  of  ammonium  hydroxide  (?).     Shake  the 
mixture  with  air,  and  note  any  changes  (?).     Give  the  name  and 
the  formula  of  the  first  precipitate  (?)  and  of  the  final  product 

(?). 

d.  Reduction  of  a  Ferric  Compound.    Dilute  some  ferric 
chloride  solution.     Through  half  of  it  bubble  some  hydrogen 
sulphide,  made  (Ex.  44  a)  in  a  test-tube  provided  with  a  1-hole 
stopper  and  delivery  tube  (?).     Test  small  portions  until  the 
liquid  no  longer  gives  the  reactions  for  a  ferric  salt.     The  pre- 
cipitate is  sulphur.     What  change  has  the  ferric-ion  undergone? 

e.  Boil  the  other  half  of  the  ferric  chloride  solution  with  iron 
powder  for  several  minutes,  filter,  and  test  quickly  for  ferrous- 
ion  (?).    Write  the  equation  [496]. 


112    SEPARATION  OF  LEAD,  MERCURY  AND  SILVER 

EXERCISE  90 
COMPOUNDS  OF  LEAD.    WHITE  LEAD 

Object:   To  make  white  lead,  and  to  learn  the  properties  of  three 

other  compounds  of  lead. 
Apparatus:   Test-tubes.     90  c.c.  bottle,  2-hole  stopper,  L-,  thistle, 

and  delivery  tubes. 
Materials:   Acetic  acid  (dil.  6  N).    Lead  monoxide.     Hydrochloric 

acid    (dil.).     Marble.     Lead   nitrate    (sol.).     Potassium   chro- 

mate  (sol.).     Potassium  iodide  (sol.). 

a.  In  a  test-tube,  take  5  c.c.  of  acetic  acid,  and  on  a  piece 
of  paper  about  3  c.c.  of  lead  monoxide.     Boil  the  acid,  and  add 
the  lead  oxide  a  very  little  at  a  time,  noting  what  becomes  of 
it  (?).    Finally  add  more  water,  boil,  and  filter  to  get  rid  of  any 
unused  lead  oxide. 

Since  the  oxide  interacts  with  acids,  to  what  class  of  oxides 
does  it  belong  [503]?    What  substance  is  here  formed? 

b.  Generate  carbon  dioxide  (Ex.  59  a)  and  lead  the  gas  through 
the  filtrate  (?).    Give  the  name  and  formula  of  the  precipitate 
[604]  (?).    What  industry  uses  this  process? 

c.  Dilute  5  c.c.  of  lead  nitrate  solution  and  divide  it  into  three 
parts.     To  one  add  dilute  hydrochloric  acid  (?).    Write  the 
equation  and  name  each  substance  (?).    Indicate  which  is  the 
insoluble  one  [505]  (?). 

d.  To  the  second  add  potassium  chromate  solution  (?)  and 
answer  the  same  question  as  in  c. 

e.  To  the  third  add  potassium  iodide  solution  (?)  and  answer 
the  same  question  as  in  c.    Boil  the  mixture,  allow  it  to  settle, 
pour  off  the  liquid  into  a  clean  test-tube  and  observe  it  as  it 
cools  (?).    Explain  (?). 

EXERCISE  91 

SEPARATION  OF  LEAD,  MERCURY  AND  SILVER 
(Metals  of  Group  I) 

Object:  To  learn  how  to  use  the  properties  of  the  compounds  of  lead, 
mercury  (ous) ,  and  silver  for  the  purpose  of  separating  these  ele- 
ments from  a  mixture  and  identifying  each  when  separated. 

Apparatus:  Test-tubes.    Funnel. 


SEPARATION  OF  LEAD,  MERCURY  AND  SILVER       113 

Materials:  Lead  nitrate  (sol.).  Hydrochloric  acid  (dil.)-  Potas- 
sium chromate  (sol.).  Mercurous  nitrate  (sol.).  Ammonium 
hydroxide.  Silver  nitrate  (sol.).  Filter  paper.  Nitric  acid 
(cone.).  Litmus  papers.  Hydrochloric  acid  (cone.).  Copper 
foil  (5  x  50  mm.).  Unknowns. 

a.  Lead  Chloride.    Dilute  2  c.c.  of  lead  nitrate  solution  with 
5  c.c.  of  water  and  add  dilute  hydrochloric  acid,  drop  by  drop, 
shaking  between  drops  and  allowing  the  precipitate  (name  it?) 
to  settle,  until  the  next  drop  produces  no  further  precipitation. 

b.  When  the  precipitate  has  settled,  pour  away  the  liquid 
(what  does  this  contain  ?).     Shake  the  precipitate  with  a  little 
distilled  water,  and  allow  it  to  settle,  and  again  pour  off  the 
liquid.     Now  boil  the  precipitate  with  distilled  water  (?). 

c.  Divide  the  solution  into  two  parts.     Set  one  aside  for  later 
observation  (?).    To  the  other  add  potassium  chromate  solu- 
tion (?).     How  should  you  recognize  a  soluble  salt  of  lead? 

d.  Mercurous  Chloride.    Repeat  a  and  b,  using  2  c.c.  of  mer- 
curous  nitrate  solution  (?).    Does  the  precipitate  (name  it  ?) 
dissolve  on  boiling? 

Add  to  the  suspended  precipitate  some  ammonium  hydroxide 
[537]  (?).  How  should  you  recognize  a  soluble  mercurous  salt? 

e.  Silver  Chloride.     Repeat  a  and  6,  using  2  c.c.  of  silver 
nitrate  solution  (?).    Does  the  precipitate  dissolve  on  boiling? 

Divide  the  suspended  precipitate  into  two  parts.  Set  one 
in  the  strongest  light  available  and  examine  it  later  (?). 

To  the  other  part  add  ammonium  hydroxide  [521]  (?). 

/.  The  Separation.  Mix  in  one  test-tube  2  c.c.  each  of  solu- 
tions of  lead  nitrate,  mercurous  nitrate,  and  silver  nitrate. 
Dilute  with  water  and  add  dilute  hydrochloric  acid  until  the 
precipitation  is  complete.  Filter,  and  wash  the  precipitate  with 
a  little  cold  water. 

To  separate  the  lead  pour  50  c.c.  of  boiling  water  through  the 
filter,  taking  care  to  pour  it  over  every  part  of  the  precipitate. 
Which  compound  will  dissolve?  Test  the  filtrate  for  the  pres- 
ence of  this  compound  (?). 

Next,  to  separate  the  silver,  dilute  5  c.c.  of  ammonium  hy- 
droxide with  water,  place  a  clean  vessel  under  the  funnel,  and 
pour  the  solution  over  the  precipitate  (?).  What  do  you  ob- 
serve? Which  compound  is  now  dissolved  (?)  and  which  re- 
mains upon  the  filter? 


114         DISPLACEMENT  OF  METALS.      COUPLES 

A  ..  - ' 

To  the  filtrate,  add  concentrated  nitric  acid,  until  the  am- 
monium hydroxide  is  neutralized  (test  on  litmus  papers)  (?). 
Name  the  precipitate,  and  summarize  the  properties  by  which 
it  may  be  recognized:  Color  (?),  crystalline  or  amorphous  (?), 
behavior  towards  ammonium  hydroxide  (?),  towards  light  (?). 
Finally,  to  get  the  residue  on  the  filter  into  solution  for  the 
purpose  of  testing  it  for  mercury,  make  a  little  aqua  regia  by 
adding  1  c.c.  of  concentrated  hydrochloric  acid  to  0.5  c.c.  of  nitric 
acid,  warm  the  mixture,  and  pour  it  on  to  the  residue.  Catch 
the  filtrate  in  a  clean  test-tube.  Dilute  the  filtrate  with  5  c.c.  of 
water  and  put  into  it  a  small  strip  of  clean  copper  foil.  After  a 
few  minutes,  wash  the  foil,  rub  it  gently,  and  examine  [517]  (?). 
g.  Obtain  an  unknown  mixture  [Instructor]  and  separate 
and  identify  the  metals  of  this  group  contained  in  it.  Re- 
member that  negative  results  must  be  reported  as  well  as  positive 
ones. 

EXERCISE  92 
DISPLACEMENT  OF  METALS.    COUPLES 

Object:  To  study  the  displacement  of  metal-ions  and  hydrogen-ion  by 
three  metals.  Also  in  f  to  observe  the  effect  of  a  foreign  metal 
on  the  displacement  of  hydrogen  from  an  acid  by  zinc,  and  thereby 
to  explain  the  qualities  and  defects  of  galvanized  iron  and  tin  plate. 

Apparatus:  Test-tubes. 

Materials:  Copper  foil.  Zinc,  sheet.  Lead,  sheet.  Sandpaper. 
Copper  wire  (No.  30).  Labels.  Lead  nitrate  (sol.).  Mer- 
curous  nitrate  (sol.).  Silver  nitrate  (sol).  Cupric  sulphate 
(sol.).  Sulphuric  acid  (dil.). 

a.  Clean  the  metals  with  sandpaper,  and  prepare  five  strips 
(5  X  30  mm.)  of  copper  foil,  six  strips  of  sheet  zinc  and  three 
strips  of  sheet  lead.    Attach  to  each,  with  the  exception  of  one 
piece  of  zinc  (reserved  for/),  a  piece  of  copper  wire  20  cm.  long. 

b.  Zinc.    In  five  test-tubes  take  5  c.c.  each  of  solutions  of  the 
nitrates  of  lead,  mercury  and  silver  and  of  cupric  sulphate  and 
dilute  sulphuric  acid.     Label  them,  noting  on  the  label  the  name, 
formula,  and  positive  ion  in  each  case.      Place  a  strip  of  zinc 
halfway  into  each  solution  and  examine  from  time  to  time  (?). 
Tabulate  the  results  of  b,  c,  and  d  as  shown  below.     Keep  the 
strips  of  zinc  for  use  again  in  /. 

c.  Lead.    In  three  test-tubes  take  5  c.c.  each  of  solutions  of 


MANGANESE  AND  CHROMIUM  115 

mercurous  nitrate,  silver  nitrate  and  cupric  sulphate  and  label 
them  as  in  b.  Place  a  strip  of  lead  halfway  into  each  solution 
and  examine  later  (?). 

d.  Copper.       Repeat  b,  using  5  strips  of  copper  (?).     Record 
negative  as  well  as  positive  results. 

METAL          SOLUTION  TAKEN       ELEMENT       SOLUTION  FORMED 
IN  STRIP    SUBSTANCE  Pos.  ION  LIBERATED  SUBSTANCE      Pos.  ION 

Zinc  Lead  nitrate  Pb++  Lead  Zinc  nitrate  Zn++ 
Etc. 

e.  For  each  positive  result  write  an  ordinary  equation,  and 
also  an  ionic  equation  [514]  (?).    When  the  result  is  negative,  ex- 
plain why  it  is  so  [54]  (?). 

/.  A  Couple.  Place  5  c.c.  of  dilute  sulphuric  acid  in  each  of 
five  test-tubes.  Take  the  sixth  strip  of  zinc  (with  no  wire)  and 
the  four  strips  of  zinc  which  in  6  have  been  immersed  in  the  salts 
(not  the  one  placed  in  the  acid),  and  immerse  each  of  them  as 
completely  as  possible  in  a  portion  of  sulphuric  acid  (?).  Do  you 
observe  any  difference  in  the  behavior  of  the  clean  strip  and  those 
partly  coated  with  metal?  Those  coated  with  a  foreign  metal 
are  called  "  couples."  Which  metal  of  the  couple  is  attacked  — 
the  more  active  or  the  less  active  one? 

Galvanized  iron  [419]  and  tin  plate  [508]  are  couples.  Name 
the  pair  of  metals  in  each  (?).  When  each  is  corroded  by  the 
chemical  action  of  water  or  acids,  which  of  the  two  metals  in  each 
case  goes  into  combination?  In  your  everyday  experience, 
which  is  more  apt  to  rust,  galvanized  iron  or  tinned  iron  (tin 
plate)?  Give  the  reason  for  what  you  have  observed  (?). 

EXERCISE  93 

MANGANESE  AND  CHROMIUM 

Object:  To  prepare  a  manganate  and  a  chr ornate.  Also  to  study  the 
relations  of  chromates,  dichromates,  and  chromic  salts. 

Apparatus:   Platinum  wire.     Test-tubes. 

Materials:  Manganese  dioxide  (powdered).  Sodium  carbonate  (an- 
hydrous). Sodium  nitrate.  Chromic  oxide.  Potassium  chro- 
mate  (sol.).  Sulphuric  acid  (cone.).  Potassium  hydroxide  (sol.). 
Litmus  papers.  Potassium  dichromate  (sol.).  Alcohol  (95%). 

a.  Sodium  Manganate.  On  a  minute  scale,  this  substance 
may  be  made  quickly  in  the  form  of  a  bead.  Mix  on  a  piece 


116      IDENTIFICATION  OF  METALS  IN  GROUP  II 

of  paper  a  few  particles  each  of  manganese  dioxide,  sodium  car- 
bonate, and  sodium  nitrate.  Bend  the  end  of  the  platinum  wire 
into  a  long,  narrow  loop.  Heat  it  and  touch  the  mixture.  Melt 
the  mass  to  a  bead  and  heat  it  in  the  oxidizing  flame  (?).  Color 
(?).  Write  the  equation  [528]  (?). 

b.  Sodium  Permanganate.    Place  the  wire,  with  the  hot  bead, 
in  a  narrow  test-tube  containing  some  water  and,  when  the  bead 
has  dissolved,  examine  the  color  of  the  solution  by  looking  down 
through  it  at  a  piece  of  paper  (?).    Now,  blow  through  a  glass 
tube  so  that  the  breath  (as  a  source  of  carbon  dioxide)  bubbles 
through  the  solution,  and  continue  until  a  change  is  observed 
(?).    Write  the  equation  [629]  (?). 

c.  Sodium  Chromate.    Repeat  a,  using   chromic  oxide  in 
place  of  manganese  dioxide.     Color  (?).    Equation  (?). 

<L  Postassium  Chromate  made  into  Bichromate.  To  some 
potassium  chromate  solution  add  a  little  concentrated  sulphuric 
acid  drop  by  drop  and  shake  [531]  (?).  Color  (?).  Write  the 
equation  and  attach  the  name  to  each  formula  (?).  What  is  the 
anhydride  (?),  and  what  the  valence  of  chromium  in  each  of  the 
compounds  [530]  ? 

e.  Potassium  Bichromate  made  into  Chromate.  To  the 
product  from  d  add  potassium  hydroxide  solution  drop  by  drop 
until  the  liquid  is  faintly  alkaline  (test  on  litmus  paper).  Color 
(?) .  Write  the  equation  and  attach  the  name  to  each  formula  (?) . 

/.  Chromic  Sulphate  from  Potassium  Bichromate .  Alcohol 
may  be  used  here  as  the  reducing  agent.  To  5  c.c.  of  potassium 
dichromate  solution  add  10  drops  of  concentrated  sulphuric  acid 
and  5  drops  of  alcohol.  Warm  the  mixture  (?).  The  strong 
green  color  is  due  to  decomposition  of  a  part  of  the  chromic  sul- 
phate (which  is  purple).  When  the  correct  proportions  are 
taken,  purple  crystals  of  chrome  alum  can  be  obtained  from  the 
liquid.  The  odor  (?)  is  that  of  aldehyde  (CH3COH),  produced 
by  oxidation  of  the  alcohol. 

What  is  the  valence  [533]  of  chromium  in  chromic  sulphate? 

EXERCISE  94 
IDENTIFICATION  OF  METALS  IN  GROUP  II 

Object :  To  learn  how  to  use  the  properties  of  the  compounds  of  lead, 
mercury  (ic),  copper,  bismuth,  cadmium,  arsenic,  antimony,  and 
tin  for  the  purpose  of  identifying  an  unknown  substance. 


IDENTIFICATION  OF  METALS  IN  GROUP  II     117 

Apparatus:  Test-tubes.  Funnel.  Hydrogen  sulphide  generator 
(Ex.  44). 

Materials:  Lead  nitrate.  Mercuric  sulphate.  Cupric  sulphate. 
Bismuth  nitrate.  Cadmium  chloride.  Arsenic  trioxide.  Anti- 
mony trichloride.  Stannous  chloride.  Hydrochloric  acid  (dil. 
and  cone.).  Ferrous  sulphide  (small  lumps).  Nitric  acid  (dil. 
and  cone.).  Ammonium  sulphide  (yellow  solution).  Sulphuric 
acid  (dil.).  Tin  (scrap).  Ammonium  hydroxide  (sol.).  Un- 
knowns. 

a.  Lead  Nitrate.    Dissolve  1  g.  of  lead  nitrate  crystals  in  100 
g.  water,  and  add  10  c.c.  of  dilute  hydrochloric  acid.    Why  is  no 
precipitate  obtained  (see  Ex.  91)?    Now  pass  hydrogen  sulphide 
gas  through  a  portion  of  the  solution,   contained  in  a   test- 
tube  (?).     Boil,  and  add  a  few  drops  of  cone,  nitric  acid  (?). 
To  a  second  portion,  in  another  tube,  add  dilute  sulphuric 
acid  (?). 

b.  Mercuric  Sulphate.    Dissolve  1  g.  In  100  g.  water,  and 
add  10  c.c.  of  dilute  hydrochloric  acid  (?).     Now  pass  hydrogen 
sulphide  gas  through  a  portion  of  the  solution  (color  changes?). 
When  no  further  action  takes  place,  boil  and  add  a  few  drops  of 
cone,  nitric  acid  (?). 

c.  Cupric  Sulphate.      Dissolve  1  g.  in  100  g.  water  (color?), 
and  add  10  c.c.  of  dilute  hydrochloric  acid.     Pass  hydrogen 
sulphide  through  a  portion  of  the  solution  (?).     Boil,  and  add 
a  few  drops  of  cone,  nitric  acid  (?).  Add  dilute  sulphuric  acid  (?). 
Add  ammonium  hydroxide  drop  by  drop  (?)  until  no  further 
action  takes  place  [612]. 

d.  Bismuth  Nitrate.      Dissolve  1  g.  in  100  g.  water   (?). 
Shake  well,  and  to  a  portion  add  a  few  drops  of  cone,  nitric 
acid  (?)  [327].     Dilute  this  portion  again  with  a  large  amount 
of  water  (?).     To  another  portion  add  cone,  hydrochloric  acid 
drop  by  drop  until  clear  (?),  and  pass  hydrogen  sulphide  gas 
through  the  solution  (?).     Boil,  and  add  a  few  drops  of  cone, 
nitric  acid  (?).    Add  dilute  sulphuric  acid  (?).    Add  ammonium 
hydroxide  until  alkaline  (?) 

e.  Cadmium  Chloride.    Dissolve   1  g.  in  100  g.  water,  and 
add  10  c.c.  of  dilute  hydrochloric  acid.    Pass  hydrogen  sulphide 
through  a  portion  of  the  solution  (?).    Filter  and  wash  the 
precipitate,  first  with  water,  then  with  yellow  ammonium  sul- 
phide (?). 


118     IDENTIFICATION  OF  METALS  IN  GROUP  III 

/.  Arsenic  Trioxide.  Try  to  dissolve  1  g.  in  100  g.  water  (?). 
Now  add  10  c.c.  of  dilute  hydrochloric  acid  (?).  Pass  hydrogen 
sulphide  through  a  portion  of  the  solution  (?).  Filter  and  wash 
the  precipitate,  first  with  water,  then  with  yellow  ammonium 
sulphide  (?).  To  the  resulting  solution  add  dilute  hydrochloric 
acid  (?).  Allow  the  precipitate  to  settle,  and  decant  off  the 
solution.  To  the  precipitate  add  concentrated  hydrochloric 
acid,  and  boil  (?). 

g.  Antimony  Trichloride.  Dissolve  1  g.  in  100  g.  water 
(?).  Shake  well,  and  add  cone,  hydrochloric  acid  drop  by  drop 
until  clear  (?).  Dilute  a  portion  with  a  large  amount  of  water 
(?).  Through  another  portion  of  the  solution  pass  hydrogen 
sulphide  gas  (?).  Filter  and  wash 'the  precipitate,  first  with 
water,  then  with  yellow  ammonium  sulphide  (?).  To  the  re- 
sulting solution  add  dilute  hydrochloric  acid  (?).  Allow  the 
precipitate  to  settle,  decant  off  the  solution,  add  to  the  precipi- 
tate concentrated  hydrochloric  acid,  and  boil  (?).  Cool  and 
dilute  the  solution,  and  place  in  it  a  piece  of  bright  tin  (?)  [54], 

h.  Stannous  Chloride.      Treat  as  in  g  above. 

j.  Identification  of  an  Unknown.  Obtain  an  unknown 
substance  containing  a  metal  in  Group  II  [Instructor].  Dissolve 
1  g.  in  100  g.  water  (?).  Note  color  of  solution.  If  solution  is 
clear  add  10  c.c.  dilute  hydrochloric  acid;  if  it  is  not  clear  add 
concentrated  hydrochloric  acid  drop  by  drop.  Examine  any 
precipitate  which  persists  for  lead  as  in  Ex.  91.  Pass  hydrogen 
sulphide  gas  through  a  portion  of  the  solution.  Note  color  of 
precipitate.  Filter  and  wash  with  water,  then  with  yellow 
ammonium  sulphide. 

A.  Precipitate  is  Insoluble.    HgS,  CuS,  PbS,  Bi2S3,  CdS. 

B.  Precipitate  is  Insoluble.    As2S3,  Sb2S3,  SnS. 

From  the  earlier  parts  of  the  exercise  the  student  will  be  able 
to  deduce  for  himself  the  remaining  stages  of  the  analysis. 

EXERCISE  95 
IDENTIFICATION  OF  METALS  IN  GROUP  III 

Object:  To  learn  how  to  use  the  properties  of  the  compounds  of 
aluminium,  chromium,  iron,  cobalt,  nickel,  manganese  and  zinc 
for  the  purpose  of  identifying  an  unknown  substance. 

Apparatus :  Test-tubes.     Hydrogen  sulphide  generator  (Ex.  44). 


IDENTIFICATION  OF  METALS  IN  GROUPS  IV  AND  V  119 

Materials:  Aluminium  sulphate.  Chrome  alum.  Ferrous  sul- 
phate. Ferric  sulphate.  Nickel  sulphate.  Cobaltous  chloride. 
Manganous  sulphate.  Zinc  sulphate.  Ammonium  chloride 
(sol.).  Ammonium  hydroxide  (sol.).  Potassium  ferricyanide 
(sol.).  Ferrous  sulphide  (small  lumps).  Sodium  hydroxide 
(sol.). 

a.  Aluminium  Sulphate.    Dissolve  1  g.  in  100  g.  water,  and 
to  a  portion  of  the  solution  add  first  ammonium  chloride  (?), 
then    ammonium    hydroxide    (?).    To    another    portion    add 
sodium  hydroxide,  drop  by  drop  (?). 

b.  Chrome  Alum.    Same    procedure  as  in  a  above.    Note 
color  changes  (?). 

c.  Ferrous   Sulphate.    Dissolve  1  g.  in  100  g.  water,  and  to 
a  portion  of  the  solution  add  first  ammonium  chloride  (?),  then 
ammonium  hydroxide  (?).     To  another  portion  add  potassium 
ferricyanide  solution  (see  Ex.  89). 

d.  Ferric  Sulphate.    Same  procedure  as  in  c  above. 

e.  Nickel  Sulphate.    Dissolve  1  g.  in  100  g.  water.    Note 
color  (?).     To  a  portion  of  the  solution  add  first  ammonium 
chloride  (?),  then  ammonium  hydroxide  (?),  then  pass  hydrogen 
sulphide  gas  through  (?).    To  another  portion  add  sodium  hy- 
droxide, drop  by  drop  (?). 

/.  Cobalt  Chloride.    Same  procedure  as  in  e  above. 

g.  Manganous  Sulphate.    Same  procedure  as  in  e  above. 

h.  Zinc  Sulphate.    Same  procedure  as  in  e  above. 

j.  Identification  of  an  Unknown.  Obtain  an  unknown  sub- 
stance containing  a  metal  in  Group  III  [Instructor].  Dis- 
solve 1  g.  in  100  g.  water,  and  plan  a  scheme  of  analysis _from  the 
results  of  tests  a  to  h  above. 

EXERCISE  96 
IDENTIFICATION  OF  METALS  IN  GROUPS  IV  AND  V 

Object:  To  learn  how  to  use  the  properties  of  the  compounds  of  cal- 
cium, strontium,  barium,  magnesium,  ammonium,  potassium  and 
sodium  for  the  purpose  of  identifying  an  unknown  substance. 

Apparatus :  Test-tubes.     Iron  or  platinum  wire.     Cobalt  glass. 

Materials:  Chlorides  of  calcium,  strontium,  barium,  magnesium, 
ammonium,  potassium  and  sodium.  Ammonium  chloride  (sol.). 
Ammonium  hydroxide  (sol.).  Ammonium  carbonate  (sol.). 
Ammonium  phosphate  (sol.).  Sodium  hydroxide  (sol.). 


120  RECOGNITION  OF  SUBSTANCES  III 

a.  Calcium  Chloride.    Dissolve  1  g.  in  100  g.  water.    Add 
ammonium  chloride  (?),  then,  ammonium  hydroxide  (?),  then 
ammonium  carbonate  (?).    Try  also  flame  test  (Ex.  71). 

b.  Strontium  Chloride.    Same  procedure  as  in  a  above. 

c.  Barium  Chloride.    Same  procedure  as  in  a  above. 

d.  Magnesium  Chloride.     Dissolve  1  g.  in   100  g.  water. 
To  one  portion  add  ammonium  hydroxide  (?).    To  a  second 
portion  add  ammonium  chloride  (?),  then  ammonium  hydroxide 
(?),  then  ammonium  carbonate  (?),  then  ammonium  phosphate 

(?)• 

e.  Ammonium  Chloride.     Dissolve  1  g.  in  100  g.  water. 
Add  sodium  hydroxide,  and  boil  (?).     (See  Ex.  51  /). 

/.  Potassium  Chloride.     Try  flame  test  as  in  Ex.  71. 

g.  Sodium  Chloride.    Try  flame  test  as  in  Ex.  71. 

h.  Identification  of  an  Unknown.  Obtain  an  unknown  sub- 
stance containing  a  metal  in  Groups  IV  and  V  [Instructor]. 
Dissolve  1  g.  in  100  g.  water,  and  plan  a  scheme  of  analysis  from 
the  results  of  tests  a  to  g  above. 


EXERCISE  97 

RECOGNITION  OF  SUBSTANCES  III 
(Metallic  Elements) 

Object:  To  use  the  properties  studied  in  previous  exercises  for  the 
purpose  of  identifying  the  metallic  element  in  an  unknown  com- 
pound. 

Apparatus:  Test-tubes.  Funnel.  Hydrogen  sulphide  generator. 
Platinum  wire.  Evaporating  dish.  Glass  rod.  Cobalt  glass. 

Materials:  Unknowns.    Solutions  used  in  Exercises  91,  94,  95,  96. 

a.  Obtain  [Instructor]  an  unknown  solid  substance. 

b.  External  Examination.    Record  the  state  (?),  color  (?), 
luster,  if  any  (?),  crystalline  form  (?),  odor  (?). 

c.  Solubility  and  Reaction  of  the  Solution  [536].      Repeat 
Ex.  68  c  (?). 

d.  If  the  unknown  is  soluble  in  water,  proceed  at  once  as  in 
e  below.      If  it  is  insoluble  in  water,  try  to  bring  it  into  solu- 
tion by  boiling  successively  with  dilute  nitric  acid  (?),  concen- 
trated nitric  acid  (?),  and  aqua  regia  (?).     In  case  it  dissolves, 
evaporate  off  the  excess  of  acid  and  proceed  as  in  e.    The  only 


RECOGNITION   OF   SUBSTANCES   III  121 

common  substances  which  are  still  insoluble  are:  the  sulphates 
of  lead,  strontium  and  barium;  some  silicates;  calcium  fluoride; 
silver  chloride  (soluble  in  ammonia). 

Fuse  with  sodium  carbonate  in  a  crucible,  cool,  extract  with 
water,  and  filter.  The  residue  contains  the  positive  radical  of 
the  unknown  as  carbonate,  and  may  be  analyzed  for  this  as  in 
e,  after  dissolving  in  dilute  nitric  acid. 

e.  To  a  portion  of  the  solution  of  the  unknown  add  dilute 
hydrochloric  acid.  If  a  precipitate  is  obtained,  examine  as  in 
Ex.  91. 

/.  If  no  precipitate  is  obtained  with  dilute  hydrochloric  acid, 
pass  hydrogen  sulphide  through  the  same  portion  of  the  solution. 
If  a  precipitate  is  now  obtained,  examine  as  in  Ex.  94  j. 

g.  If  no  precipitate  is  obtained  with  hydrogen  sulphide,  boil 
the  solution  to  expel  all  hydrogen  sulphide,  and  add  a  few  drops 
of  concentrated  nitric  acid  to  oxidize  any  ferrous  salt  to  the 
ferric  state.  Then  proceed  as  in  Ex.  95  j. 

h.  If  still  no  precipitate  has  been  obtained,  proceed  as  in 
Ex.  96  h. 

j.  Report.  State  your  conclusion,  with  the  reasons  therefor 
(?).  Also,  show  that  the  conclusion  is  in  harmony  with  the 
observations  recorded  under  6  and  c  (?). 

k.  The  Negative  Radical  in  the  unknown  should  now  be 
identified  by  the  plan  outlined  and  detailed  in  Exercises  67  and 
68.  Report  as  in  j. 


122 


APPENDIX 


APPENDIX 
I.  Tension  of  Aqueous  Vapor 


Temp.  C. 

Press,  mm. 

Temp.  C. 

Press,  mm. 

Temp.  C. 

Press,  mrn. 

10 

.   9.2 

18 

15.4 

26 

25.1 

11 

9.8 

19 

16.3 

27 

26.5 

12 

10.5 

20 

17.4 

28 

28.1 

J3 

11  2 

21 

18.5 

29 

29.8 

14 

11.9 

22 

19.7 

30 

31.5 

15 

12.7 

23 

20.9 

31 

33.4 

16 

13.5 

24 

22.2 

32 

35.4 

17 

14.4 

25 

23.6 

APPENDIX  123 

II.  Fraction  Ionized  in  0.1  N  Solutions  at  18° 

ACIDS 

Nitric  acid  (H+NOs-) 0.92 

Sulphuric  acid  (2H+,SO4=) 0.61 

Oxalic  acid  (H+,HC204-) 0.50 

Phosphoric  acid  (H+HjPOr) 0.27 

Hydrofluoric  acid  (H+F-) 0.085 

Carbonic  acid  (H+HCOr) 0.0017 

Hydrosulphuric  acid  (H+HS-)  .    .    . 0.0007 

Boric  acid  (H+,H2BO3-) 0.0001 

BASES 

Sodium  hydroxide  (Na+OH-) 0.91 

Potassium  hydroxide  (K+,OH-) 0.91 

Barium  hydroxide  (Ba++,2OH-) 0.77 

Ammonium  hydroxide  (NH4+,OH-)      0.013 

SALTS 

Potassium  chloride  (K+C1-) 0.86 

Sodium  chloride  (Na+Cl-) 0.85 

Potassium  fluoride  (K+,F~) 0.85 

Sodium  nitrate  (Na+,NOr)    . .    .  0.83 

Silver  nitrate  (Ag+,NO3-) 0.81 

Barium  chloride  (Ba++,2Cl-) 0.76 

Sodium  sulphate  (2Na+,SO4=)    .    ...... 0.70 

Zinc  sulphate  (Zn++,SO4=)  .    .    . 0.40 

Copper  sulphate  (Cu++,SO4=) ,    .  0.40 

Mercuric  chloride  (Hg++,2Cl-)   ............    <0. 01 

III.  Apparatus  —  Individual 

Beakers  (2),  100  c.c.,  300  c.c.  Deflagrating  spoon,  small. 

Bottle,     wide-mouth,     90     c.c.  Dropper  (medicine). 

Mouth  to  fit  No.  5  stopper.  Evaporating    dish     (porcelain), 
Bottle,  narrow-mouth,  2  1.  125  c.c. 

Bottles  (3),  wide-mouth,  250  c.c.  File,  triangular. 

Bunsen  burner.  Filter  paper,  cut,  10  cm. 

Burette  (Mohr's)  25  c.c.  Flask,  200  c.c.     Neck  to  fit  No. 
Burette  clamp  (for  stand) .  3  stopper. 

Cardboard,  10  cm.  sq.  Funnel,  7  cm.  (O.D.*). 

Crucible  (porcelain),  25  c.c.  Glass  plates  (3),  8  cm. 

*  O.D.  =  outside  diameter.         I.D.  =  inside  diameter. 


124 


APPENDIX 


Glass  rod,  2.5  mm.  (O.D.). 

Glass  tubing,  6.5.  mm.  (O.D.). 

Graduated  cylinder,  50  c.c. 

Mortar  (porcelain),  10  cm.  (O. 
D.),  pestle. 

Pinchclamps  (2). 

Platinum  wire  (mounted),  No. 
28,  7  cm. 

Pneumatic  trough,  with  shelf  or 
support  for  bottles.  Stone- 
ware milk  pan  or  agate  pan 
about  12  X  4  inches  serves 
admirably. 

Retort  (glass  stopper),  150  c.c. 

Rubber  stopper,  No.  5,  2-hole, 
for  wide  test-tube  and  90 
c.c.  bottle. 

Rubber  stopper  No.  3,  1-hole, 
for  hard-glass  test-tube  and 
200  c.c.  flask. 

Rubber  stopper  No.  2,  1-hole, 
for  test-tube. 


Rubber  gas  tubing,  7  mm.  (I.D.), 

60cm. 
Rubber  tubing    (pure   gum),    5 

mm.  (I.D.),  30  cm. 
Stand,  rod  50  cm.,  1  ring  9-10 

cm. 
Taper. 

Test-tube  (1)  15X2  5  cm.  (I.D.). 
Test-tube  (1),  hard  glass,  15  X 

2.2.  cm.  (I.D.). 
Test-tubes     (6)     15  X  1.8    cm. 

(I.D.). 
Test-tubes    (12)    10  X  1.2    cm. 

(I.D.). 

Test-tube  brush. 
Test-tube  rack. 
Thistle  tube,  small. 
Triangle  (pipe  stem). 
Watch-glasses  (2),  5  cm.,  8  cm. 
Wing  top  (for  burner). 
Wire,  iron,  No.  26,  20  cm. 
Wire  gauze,  iron,  10  cm. 


IV.  Apparatus  —  General 


Balance.  Load  100  g.,  agate 
planes  and  agate  knife  edges 
in  glass  case,  without  rider- 
beam  (one  to  ten  students). 

Barometer. 

Bottles,  square,  25  c.c. 

Cobalt  glasses,  10  X  5  cm. 

Corks  to  fit  test-tubes  (1.8  cm. 
I.D.),  2  1.  bottle,  and  wide- 
mouth  bottles. 

Cork-borers. 

File,  round. 

Graduated  cylinders,  500  c.c. 

Kipp's  generator. 

Lens  (Coddington). 

Magnet. 


Meter  stick. 

Paper.  Roll,  smooth,  colored 
(to  prevent  use  for  writing) . 

Pipettes,  20  c.c. 

Pliers,  cutting. 

Thermometers,  —  10°  to  150°. 

Thread. 

Trip  scales  with  rider  (0-5  g.) 
and  weights  (5  g.  -  1000  g.) 

Waste  jars. 

Weights.  Good  grade  labora- 
tory weights,  1  mg.  to  50 
g.,  fractional  weights  in 
divided  compartments  under 
glass  cover,  all  in  wooden 
with  hinged  cover. 


APPENDIX 


125 


V.  Materials 


Acid,  acetic. 

formic. 
Acid,  hydrochloric,  cone 

nitric,  cone. 
Acid,  orthophosphoric 

oxalic. 

pyrogallic. 

sulphuric,  cone. 
Acid  Green  (or  Eosin). 
Alcohol,  amyl. 

ethyl,  95%. 

Albumen,  dry  com'l.  egg. 
Alizarin  paste  (20%). 
Almonds. 
Aluminium,  wire. 
Aluminium  sulphate. 
Ammonium  carbonate. 

chloride. 

hydroxide,  com'l. 

molybdate. 

nitrate. 

oxalate. 

phosphate. 

sulphate. 

sulphide. 

Antimony  trichloride. 
Apples. 

Arsenic  trioxide. 
Asbestos,  long  fiber. 

paper. 

wool. 
Barium  chloride. 

hydroxide. 
Benzene. 
Bismuth  nitrate. 
Bleaching  powder. 
Borax. 
Bromine. 
Calcium  chloride. 


Calcium. 
Calcium  carbide. 

carbonate  (marble  chips). 
Calcium,  carbonate  (powdered). 

chloride  (granulated) . 

oxide  (quicklime). 

phosphide. 

sulphate  (gypsum). 

sulphate  (powdered). 
Carbon  disulphide,  commercial. 

tetrachloride. 

Charcoal,  bone  (powdered). 
Charcoal,  wood  (splinters). 

wood  (powdered) 
Chromic  oxide. 
Chromic  alum. 
Chrysophenin. 
Clay. 
Cloth,  cheese. 

colored  calico. 

white  cotton. 

white  flannel. 

white  mixed  goods 
Coal,  bituminous. 
Cobalt  chloride. 
Copper,  foil. 

shavings. 

wire,  No.  30. 
Cottonseed  oil. 
Cupric  oxide  (powdered). 

sulphate. 

Eosin  (or  Acid  Green). 
Ether,  ethyl. 
Fat. 
Ferric  chloride. 

oxide  (powdered). 
Ferrous  chloride 

sulphate. 
Ferrous  sulphide. 


126 


APPENDIX 


Flour. 

Formaldehyde  (sol.). 

Gasoline. 

Gelatine  (flakes). 

Glucose,  brewers,  cryst. 

Graphite. 

Iodine. 

Iron,  nails. 

powder. 

wire,  No.  20. 
Kerosene  oil. 
Labels. 
Lead,  sheet. 
Lead  dioxide 

monoxide. 

nitrate. 

Lithium  chloride. 
Litmus  paper,  blue  and  red. 

sol.,  neutral. 
Logwood. 
Magnesium,  ribbon. 

wire. 

Magnesium     carbonate     (pow- 
dered) . 

chloride. 

Manganese  dioxide  (powdered). 
Manganous  sulphate. 
Matches. 
Meat. 

Mercuric  sulphate. 
Mercurous  chloride. 

nitrate. 
Mercury. 

Methyl  acetate,  commercial. 
Milk. 
Molasses. 

Nickel,  powder  (reduced). 
Nickel  sulphate. 
Paraffin. 

Phenolphthalein . 
Phosphorus,  red. 


Phosphorus,  white. 
Pinks,  or  grass  or  leaves. 
Potassium  bitartrate. 

bromide. 

chlorate. 

chloride. 

chromate. 

dichromate. 

ferricyanide. 

ferrocyanide. 

hydroxide. 

iodide. 

permanganate. 

sulphate. 

thiocyanate. 
Potassium-sodium  tartrate  (Ro- 

chelle  Salt). 
Rosin  (powdered). 
Rubber  bands  (small). 
Sand. 


Silver  nitrate. 
Soap,  castile. 

ivory. 
Soda  lime. 
Sodium  acetate. 

bicarbonate. 
Sodium  bisulphate,  commercial. 

bisulphite. 

carbonate  (anhyd.). 

carbonate  (cryst.) 

chloride. 

hydroxide. 

nitrate. 

peroxide. 

phosphate. 

Sodium,  sulphate  (cryst.) 
Stannic  oxide. 
Stannous  chloride. 
Starch. 
Strontium  chloride. 


APPENDIX  127 

Sugar,  milk.  Wood,  sawdust  and  chips. 

Sugar,  ordinary  (sucrose).  Wood,  splints  (tobacconists') 

Sulphur,  flowers.  Woolen  yarn. 

roll.  Yeast. 

Tin,  foil  (lead  free).  Zinc,  dust. 

gran.  gran. 

Toluene  sheet. 

Vinegar  (white).  Zinc  oxide. 


QD45  Smith 
S64k    A 


A. 
laboratory 


D4500 
outline  of 


.\}£,&                 OJILJ. 
1 


ill  bt?  1*1 


LIBRARY 

COLLEGE   OF   DENTISTRY 
UNIVERSITY   O^  CALIFORNIA 


